forked from Minki/linux
231c807a60
Pull scheduler updates from Thomas Gleixner:
"Third more careful attempt for this set of fixes:
- Prevent a 32bit math overflow in the cpufreq code
- Fix a buffer overflow when scanning the cgroup2 cpu.max property
- A set of fixes for the NOHZ scheduler logic to prevent waking up
CPUs even if the capacity of the busy CPUs is sufficient along with
other tweaks optimizing the behaviour for asymmetric systems
(big/little)"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/fair: Skip LLC NOHZ logic for asymmetric systems
sched/fair: Tune down misfit NOHZ kicks
sched/fair: Comment some nohz_balancer_kick() kick conditions
sched/core: Fix buffer overflow in cgroup2 property cpu.max
sched/cpufreq: Fix 32-bit math overflow
10710 lines
284 KiB
C
10710 lines
284 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
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*
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* Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*
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* Interactivity improvements by Mike Galbraith
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* (C) 2007 Mike Galbraith <efault@gmx.de>
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*
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* Various enhancements by Dmitry Adamushko.
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* (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
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*
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* Group scheduling enhancements by Srivatsa Vaddagiri
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* Copyright IBM Corporation, 2007
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* Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
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*
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* Scaled math optimizations by Thomas Gleixner
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* Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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*
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* Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
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*/
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#include "sched.h"
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#include <trace/events/sched.h>
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/*
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* Targeted preemption latency for CPU-bound tasks:
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*
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* NOTE: this latency value is not the same as the concept of
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* 'timeslice length' - timeslices in CFS are of variable length
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* and have no persistent notion like in traditional, time-slice
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* based scheduling concepts.
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*
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* (to see the precise effective timeslice length of your workload,
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* run vmstat and monitor the context-switches (cs) field)
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*
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* (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
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*/
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unsigned int sysctl_sched_latency = 6000000ULL;
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static unsigned int normalized_sysctl_sched_latency = 6000000ULL;
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/*
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* The initial- and re-scaling of tunables is configurable
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*
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* Options are:
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*
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* SCHED_TUNABLESCALING_NONE - unscaled, always *1
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* SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
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* SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
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*
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* (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
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*/
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enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
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/*
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* Minimal preemption granularity for CPU-bound tasks:
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*
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* (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*/
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unsigned int sysctl_sched_min_granularity = 750000ULL;
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static unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
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/*
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* This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
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*/
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static unsigned int sched_nr_latency = 8;
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/*
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* After fork, child runs first. If set to 0 (default) then
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* parent will (try to) run first.
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*/
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unsigned int sysctl_sched_child_runs_first __read_mostly;
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/*
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* SCHED_OTHER wake-up granularity.
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*
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* This option delays the preemption effects of decoupled workloads
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* and reduces their over-scheduling. Synchronous workloads will still
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* have immediate wakeup/sleep latencies.
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*
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* (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*/
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unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
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static unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
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const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
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#ifdef CONFIG_SMP
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/*
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* For asym packing, by default the lower numbered CPU has higher priority.
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*/
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int __weak arch_asym_cpu_priority(int cpu)
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{
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return -cpu;
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}
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/*
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* The margin used when comparing utilization with CPU capacity:
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* util * margin < capacity * 1024
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*
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* (default: ~20%)
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*/
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static unsigned int capacity_margin = 1280;
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#endif
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#ifdef CONFIG_CFS_BANDWIDTH
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/*
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* Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
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* each time a cfs_rq requests quota.
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*
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* Note: in the case that the slice exceeds the runtime remaining (either due
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* to consumption or the quota being specified to be smaller than the slice)
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* we will always only issue the remaining available time.
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*
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* (default: 5 msec, units: microseconds)
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*/
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unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
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#endif
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static inline void update_load_add(struct load_weight *lw, unsigned long inc)
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{
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lw->weight += inc;
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lw->inv_weight = 0;
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}
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static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
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{
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lw->weight -= dec;
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lw->inv_weight = 0;
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}
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static inline void update_load_set(struct load_weight *lw, unsigned long w)
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{
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lw->weight = w;
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lw->inv_weight = 0;
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}
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/*
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* Increase the granularity value when there are more CPUs,
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* because with more CPUs the 'effective latency' as visible
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* to users decreases. But the relationship is not linear,
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* so pick a second-best guess by going with the log2 of the
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* number of CPUs.
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*
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* This idea comes from the SD scheduler of Con Kolivas:
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*/
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static unsigned int get_update_sysctl_factor(void)
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{
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unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
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unsigned int factor;
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switch (sysctl_sched_tunable_scaling) {
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case SCHED_TUNABLESCALING_NONE:
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factor = 1;
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break;
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case SCHED_TUNABLESCALING_LINEAR:
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factor = cpus;
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break;
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case SCHED_TUNABLESCALING_LOG:
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default:
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factor = 1 + ilog2(cpus);
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break;
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}
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return factor;
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}
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static void update_sysctl(void)
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{
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unsigned int factor = get_update_sysctl_factor();
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#define SET_SYSCTL(name) \
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(sysctl_##name = (factor) * normalized_sysctl_##name)
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SET_SYSCTL(sched_min_granularity);
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SET_SYSCTL(sched_latency);
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SET_SYSCTL(sched_wakeup_granularity);
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#undef SET_SYSCTL
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}
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void sched_init_granularity(void)
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{
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update_sysctl();
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}
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#define WMULT_CONST (~0U)
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#define WMULT_SHIFT 32
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static void __update_inv_weight(struct load_weight *lw)
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{
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unsigned long w;
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if (likely(lw->inv_weight))
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return;
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w = scale_load_down(lw->weight);
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if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
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lw->inv_weight = 1;
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else if (unlikely(!w))
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lw->inv_weight = WMULT_CONST;
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else
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lw->inv_weight = WMULT_CONST / w;
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}
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/*
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* delta_exec * weight / lw.weight
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* OR
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* (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
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*
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* Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
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* we're guaranteed shift stays positive because inv_weight is guaranteed to
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* fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
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*
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* Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
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* weight/lw.weight <= 1, and therefore our shift will also be positive.
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*/
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static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
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{
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u64 fact = scale_load_down(weight);
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int shift = WMULT_SHIFT;
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__update_inv_weight(lw);
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if (unlikely(fact >> 32)) {
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while (fact >> 32) {
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fact >>= 1;
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shift--;
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}
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}
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/* hint to use a 32x32->64 mul */
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fact = (u64)(u32)fact * lw->inv_weight;
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while (fact >> 32) {
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fact >>= 1;
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shift--;
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}
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return mul_u64_u32_shr(delta_exec, fact, shift);
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}
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const struct sched_class fair_sched_class;
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/**************************************************************
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* CFS operations on generic schedulable entities:
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*/
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#ifdef CONFIG_FAIR_GROUP_SCHED
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static inline struct task_struct *task_of(struct sched_entity *se)
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{
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SCHED_WARN_ON(!entity_is_task(se));
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return container_of(se, struct task_struct, se);
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}
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/* Walk up scheduling entities hierarchy */
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#define for_each_sched_entity(se) \
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for (; se; se = se->parent)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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return p->se.cfs_rq;
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}
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/* runqueue on which this entity is (to be) queued */
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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
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{
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return se->cfs_rq;
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}
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/* runqueue "owned" by this group */
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static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
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{
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return grp->my_q;
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}
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static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
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{
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struct rq *rq = rq_of(cfs_rq);
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int cpu = cpu_of(rq);
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if (cfs_rq->on_list)
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return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
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cfs_rq->on_list = 1;
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/*
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* Ensure we either appear before our parent (if already
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* enqueued) or force our parent to appear after us when it is
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* enqueued. The fact that we always enqueue bottom-up
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* reduces this to two cases and a special case for the root
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* cfs_rq. Furthermore, it also means that we will always reset
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* tmp_alone_branch either when the branch is connected
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* to a tree or when we reach the top of the tree
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*/
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if (cfs_rq->tg->parent &&
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cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
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/*
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* If parent is already on the list, we add the child
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* just before. Thanks to circular linked property of
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* the list, this means to put the child at the tail
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* of the list that starts by parent.
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*/
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list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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&(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
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/*
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* The branch is now connected to its tree so we can
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* reset tmp_alone_branch to the beginning of the
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* list.
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*/
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rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
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return true;
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}
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if (!cfs_rq->tg->parent) {
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/*
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* cfs rq without parent should be put
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* at the tail of the list.
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*/
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list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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&rq->leaf_cfs_rq_list);
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/*
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* We have reach the top of a tree so we can reset
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* tmp_alone_branch to the beginning of the list.
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*/
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rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
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return true;
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}
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/*
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* The parent has not already been added so we want to
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* make sure that it will be put after us.
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* tmp_alone_branch points to the begin of the branch
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* where we will add parent.
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*/
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list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch);
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/*
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* update tmp_alone_branch to points to the new begin
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* of the branch
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*/
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rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
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return false;
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}
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static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
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{
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if (cfs_rq->on_list) {
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struct rq *rq = rq_of(cfs_rq);
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/*
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* With cfs_rq being unthrottled/throttled during an enqueue,
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* it can happen the tmp_alone_branch points the a leaf that
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* we finally want to del. In this case, tmp_alone_branch moves
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* to the prev element but it will point to rq->leaf_cfs_rq_list
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* at the end of the enqueue.
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*/
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if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list)
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rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev;
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list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
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cfs_rq->on_list = 0;
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}
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}
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static inline void assert_list_leaf_cfs_rq(struct rq *rq)
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{
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SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list);
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}
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/* Iterate thr' all leaf cfs_rq's on a runqueue */
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#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
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list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
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leaf_cfs_rq_list)
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/* Do the two (enqueued) entities belong to the same group ? */
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static inline struct cfs_rq *
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is_same_group(struct sched_entity *se, struct sched_entity *pse)
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{
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if (se->cfs_rq == pse->cfs_rq)
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return se->cfs_rq;
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return NULL;
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}
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static inline struct sched_entity *parent_entity(struct sched_entity *se)
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{
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return se->parent;
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}
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static void
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find_matching_se(struct sched_entity **se, struct sched_entity **pse)
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{
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int se_depth, pse_depth;
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/*
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* preemption test can be made between sibling entities who are in the
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* same cfs_rq i.e who have a common parent. Walk up the hierarchy of
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* both tasks until we find their ancestors who are siblings of common
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* parent.
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*/
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/* First walk up until both entities are at same depth */
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se_depth = (*se)->depth;
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pse_depth = (*pse)->depth;
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while (se_depth > pse_depth) {
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se_depth--;
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*se = parent_entity(*se);
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}
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while (pse_depth > se_depth) {
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pse_depth--;
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*pse = parent_entity(*pse);
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}
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while (!is_same_group(*se, *pse)) {
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*se = parent_entity(*se);
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*pse = parent_entity(*pse);
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}
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}
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#else /* !CONFIG_FAIR_GROUP_SCHED */
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static inline struct task_struct *task_of(struct sched_entity *se)
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{
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return container_of(se, struct task_struct, se);
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}
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#define for_each_sched_entity(se) \
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for (; se; se = NULL)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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return &task_rq(p)->cfs;
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}
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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
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{
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struct task_struct *p = task_of(se);
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struct rq *rq = task_rq(p);
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return &rq->cfs;
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}
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/* runqueue "owned" by this group */
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static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
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{
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return NULL;
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}
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static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
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{
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return true;
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}
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static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
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{
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}
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static inline void assert_list_leaf_cfs_rq(struct rq *rq)
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{
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}
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#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
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for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
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|
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static inline struct sched_entity *parent_entity(struct sched_entity *se)
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{
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return NULL;
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}
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|
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static inline void
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find_matching_se(struct sched_entity **se, struct sched_entity **pse)
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{
|
|
}
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|
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#endif /* CONFIG_FAIR_GROUP_SCHED */
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|
|
static __always_inline
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void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
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|
|
/**************************************************************
|
|
* Scheduling class tree data structure manipulation methods:
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|
*/
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|
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static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
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|
{
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s64 delta = (s64)(vruntime - max_vruntime);
|
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if (delta > 0)
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max_vruntime = vruntime;
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|
|
return max_vruntime;
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}
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|
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static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
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|
{
|
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s64 delta = (s64)(vruntime - min_vruntime);
|
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if (delta < 0)
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min_vruntime = vruntime;
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|
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return min_vruntime;
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}
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|
|
|
static inline int entity_before(struct sched_entity *a,
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struct sched_entity *b)
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{
|
|
return (s64)(a->vruntime - b->vruntime) < 0;
|
|
}
|
|
|
|
static void update_min_vruntime(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct sched_entity *curr = cfs_rq->curr;
|
|
struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
|
|
|
|
u64 vruntime = cfs_rq->min_vruntime;
|
|
|
|
if (curr) {
|
|
if (curr->on_rq)
|
|
vruntime = curr->vruntime;
|
|
else
|
|
curr = NULL;
|
|
}
|
|
|
|
if (leftmost) { /* non-empty tree */
|
|
struct sched_entity *se;
|
|
se = rb_entry(leftmost, struct sched_entity, run_node);
|
|
|
|
if (!curr)
|
|
vruntime = se->vruntime;
|
|
else
|
|
vruntime = min_vruntime(vruntime, se->vruntime);
|
|
}
|
|
|
|
/* ensure we never gain time by being placed backwards. */
|
|
cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
|
|
#ifndef CONFIG_64BIT
|
|
smp_wmb();
|
|
cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* Enqueue an entity into the rb-tree:
|
|
*/
|
|
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
|
|
struct rb_node *parent = NULL;
|
|
struct sched_entity *entry;
|
|
bool leftmost = true;
|
|
|
|
/*
|
|
* Find the right place in the rbtree:
|
|
*/
|
|
while (*link) {
|
|
parent = *link;
|
|
entry = rb_entry(parent, struct sched_entity, run_node);
|
|
/*
|
|
* We dont care about collisions. Nodes with
|
|
* the same key stay together.
|
|
*/
|
|
if (entity_before(se, entry)) {
|
|
link = &parent->rb_left;
|
|
} else {
|
|
link = &parent->rb_right;
|
|
leftmost = false;
|
|
}
|
|
}
|
|
|
|
rb_link_node(&se->run_node, parent, link);
|
|
rb_insert_color_cached(&se->run_node,
|
|
&cfs_rq->tasks_timeline, leftmost);
|
|
}
|
|
|
|
static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
|
|
}
|
|
|
|
struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
|
|
|
|
if (!left)
|
|
return NULL;
|
|
|
|
return rb_entry(left, struct sched_entity, run_node);
|
|
}
|
|
|
|
static struct sched_entity *__pick_next_entity(struct sched_entity *se)
|
|
{
|
|
struct rb_node *next = rb_next(&se->run_node);
|
|
|
|
if (!next)
|
|
return NULL;
|
|
|
|
return rb_entry(next, struct sched_entity, run_node);
|
|
}
|
|
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
|
|
|
|
if (!last)
|
|
return NULL;
|
|
|
|
return rb_entry(last, struct sched_entity, run_node);
|
|
}
|
|
|
|
/**************************************************************
|
|
* Scheduling class statistics methods:
|
|
*/
|
|
|
|
int sched_proc_update_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp,
|
|
loff_t *ppos)
|
|
{
|
|
int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
unsigned int factor = get_update_sysctl_factor();
|
|
|
|
if (ret || !write)
|
|
return ret;
|
|
|
|
sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
|
|
sysctl_sched_min_granularity);
|
|
|
|
#define WRT_SYSCTL(name) \
|
|
(normalized_sysctl_##name = sysctl_##name / (factor))
|
|
WRT_SYSCTL(sched_min_granularity);
|
|
WRT_SYSCTL(sched_latency);
|
|
WRT_SYSCTL(sched_wakeup_granularity);
|
|
#undef WRT_SYSCTL
|
|
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* delta /= w
|
|
*/
|
|
static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
|
|
{
|
|
if (unlikely(se->load.weight != NICE_0_LOAD))
|
|
delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
|
|
|
|
return delta;
|
|
}
|
|
|
|
/*
|
|
* The idea is to set a period in which each task runs once.
|
|
*
|
|
* When there are too many tasks (sched_nr_latency) we have to stretch
|
|
* this period because otherwise the slices get too small.
|
|
*
|
|
* p = (nr <= nl) ? l : l*nr/nl
|
|
*/
|
|
static u64 __sched_period(unsigned long nr_running)
|
|
{
|
|
if (unlikely(nr_running > sched_nr_latency))
|
|
return nr_running * sysctl_sched_min_granularity;
|
|
else
|
|
return sysctl_sched_latency;
|
|
}
|
|
|
|
/*
|
|
* We calculate the wall-time slice from the period by taking a part
|
|
* proportional to the weight.
|
|
*
|
|
* s = p*P[w/rw]
|
|
*/
|
|
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
|
|
|
|
for_each_sched_entity(se) {
|
|
struct load_weight *load;
|
|
struct load_weight lw;
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
|
load = &cfs_rq->load;
|
|
|
|
if (unlikely(!se->on_rq)) {
|
|
lw = cfs_rq->load;
|
|
|
|
update_load_add(&lw, se->load.weight);
|
|
load = &lw;
|
|
}
|
|
slice = __calc_delta(slice, se->load.weight, load);
|
|
}
|
|
return slice;
|
|
}
|
|
|
|
/*
|
|
* We calculate the vruntime slice of a to-be-inserted task.
|
|
*
|
|
* vs = s/w
|
|
*/
|
|
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
return calc_delta_fair(sched_slice(cfs_rq, se), se);
|
|
}
|
|
|
|
#include "pelt.h"
|
|
#ifdef CONFIG_SMP
|
|
|
|
static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
|
|
static unsigned long task_h_load(struct task_struct *p);
|
|
static unsigned long capacity_of(int cpu);
|
|
|
|
/* Give new sched_entity start runnable values to heavy its load in infant time */
|
|
void init_entity_runnable_average(struct sched_entity *se)
|
|
{
|
|
struct sched_avg *sa = &se->avg;
|
|
|
|
memset(sa, 0, sizeof(*sa));
|
|
|
|
/*
|
|
* Tasks are initialized with full load to be seen as heavy tasks until
|
|
* they get a chance to stabilize to their real load level.
|
|
* Group entities are initialized with zero load to reflect the fact that
|
|
* nothing has been attached to the task group yet.
|
|
*/
|
|
if (entity_is_task(se))
|
|
sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight);
|
|
|
|
se->runnable_weight = se->load.weight;
|
|
|
|
/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
|
|
}
|
|
|
|
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
|
|
static void attach_entity_cfs_rq(struct sched_entity *se);
|
|
|
|
/*
|
|
* With new tasks being created, their initial util_avgs are extrapolated
|
|
* based on the cfs_rq's current util_avg:
|
|
*
|
|
* util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
|
|
*
|
|
* However, in many cases, the above util_avg does not give a desired
|
|
* value. Moreover, the sum of the util_avgs may be divergent, such
|
|
* as when the series is a harmonic series.
|
|
*
|
|
* To solve this problem, we also cap the util_avg of successive tasks to
|
|
* only 1/2 of the left utilization budget:
|
|
*
|
|
* util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
|
|
*
|
|
* where n denotes the nth task and cpu_scale the CPU capacity.
|
|
*
|
|
* For example, for a CPU with 1024 of capacity, a simplest series from
|
|
* the beginning would be like:
|
|
*
|
|
* task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
|
|
* cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
|
|
*
|
|
* Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
|
|
* if util_avg > util_avg_cap.
|
|
*/
|
|
void post_init_entity_util_avg(struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
struct sched_avg *sa = &se->avg;
|
|
long cpu_scale = arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq)));
|
|
long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
|
|
|
|
if (cap > 0) {
|
|
if (cfs_rq->avg.util_avg != 0) {
|
|
sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
|
|
sa->util_avg /= (cfs_rq->avg.load_avg + 1);
|
|
|
|
if (sa->util_avg > cap)
|
|
sa->util_avg = cap;
|
|
} else {
|
|
sa->util_avg = cap;
|
|
}
|
|
}
|
|
|
|
if (p->sched_class != &fair_sched_class) {
|
|
/*
|
|
* For !fair tasks do:
|
|
*
|
|
update_cfs_rq_load_avg(now, cfs_rq);
|
|
attach_entity_load_avg(cfs_rq, se, 0);
|
|
switched_from_fair(rq, p);
|
|
*
|
|
* such that the next switched_to_fair() has the
|
|
* expected state.
|
|
*/
|
|
se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
|
|
return;
|
|
}
|
|
|
|
attach_entity_cfs_rq(se);
|
|
}
|
|
|
|
#else /* !CONFIG_SMP */
|
|
void init_entity_runnable_average(struct sched_entity *se)
|
|
{
|
|
}
|
|
void post_init_entity_util_avg(struct task_struct *p)
|
|
{
|
|
}
|
|
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
|
|
{
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* Update the current task's runtime statistics.
|
|
*/
|
|
static void update_curr(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct sched_entity *curr = cfs_rq->curr;
|
|
u64 now = rq_clock_task(rq_of(cfs_rq));
|
|
u64 delta_exec;
|
|
|
|
if (unlikely(!curr))
|
|
return;
|
|
|
|
delta_exec = now - curr->exec_start;
|
|
if (unlikely((s64)delta_exec <= 0))
|
|
return;
|
|
|
|
curr->exec_start = now;
|
|
|
|
schedstat_set(curr->statistics.exec_max,
|
|
max(delta_exec, curr->statistics.exec_max));
|
|
|
|
curr->sum_exec_runtime += delta_exec;
|
|
schedstat_add(cfs_rq->exec_clock, delta_exec);
|
|
|
|
curr->vruntime += calc_delta_fair(delta_exec, curr);
|
|
update_min_vruntime(cfs_rq);
|
|
|
|
if (entity_is_task(curr)) {
|
|
struct task_struct *curtask = task_of(curr);
|
|
|
|
trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
|
|
cgroup_account_cputime(curtask, delta_exec);
|
|
account_group_exec_runtime(curtask, delta_exec);
|
|
}
|
|
|
|
account_cfs_rq_runtime(cfs_rq, delta_exec);
|
|
}
|
|
|
|
static void update_curr_fair(struct rq *rq)
|
|
{
|
|
update_curr(cfs_rq_of(&rq->curr->se));
|
|
}
|
|
|
|
static inline void
|
|
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
u64 wait_start, prev_wait_start;
|
|
|
|
if (!schedstat_enabled())
|
|
return;
|
|
|
|
wait_start = rq_clock(rq_of(cfs_rq));
|
|
prev_wait_start = schedstat_val(se->statistics.wait_start);
|
|
|
|
if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
|
|
likely(wait_start > prev_wait_start))
|
|
wait_start -= prev_wait_start;
|
|
|
|
__schedstat_set(se->statistics.wait_start, wait_start);
|
|
}
|
|
|
|
static inline void
|
|
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
struct task_struct *p;
|
|
u64 delta;
|
|
|
|
if (!schedstat_enabled())
|
|
return;
|
|
|
|
delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
|
|
|
|
if (entity_is_task(se)) {
|
|
p = task_of(se);
|
|
if (task_on_rq_migrating(p)) {
|
|
/*
|
|
* Preserve migrating task's wait time so wait_start
|
|
* time stamp can be adjusted to accumulate wait time
|
|
* prior to migration.
|
|
*/
|
|
__schedstat_set(se->statistics.wait_start, delta);
|
|
return;
|
|
}
|
|
trace_sched_stat_wait(p, delta);
|
|
}
|
|
|
|
__schedstat_set(se->statistics.wait_max,
|
|
max(schedstat_val(se->statistics.wait_max), delta));
|
|
__schedstat_inc(se->statistics.wait_count);
|
|
__schedstat_add(se->statistics.wait_sum, delta);
|
|
__schedstat_set(se->statistics.wait_start, 0);
|
|
}
|
|
|
|
static inline void
|
|
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
struct task_struct *tsk = NULL;
|
|
u64 sleep_start, block_start;
|
|
|
|
if (!schedstat_enabled())
|
|
return;
|
|
|
|
sleep_start = schedstat_val(se->statistics.sleep_start);
|
|
block_start = schedstat_val(se->statistics.block_start);
|
|
|
|
if (entity_is_task(se))
|
|
tsk = task_of(se);
|
|
|
|
if (sleep_start) {
|
|
u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
|
|
|
|
if ((s64)delta < 0)
|
|
delta = 0;
|
|
|
|
if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
|
|
__schedstat_set(se->statistics.sleep_max, delta);
|
|
|
|
__schedstat_set(se->statistics.sleep_start, 0);
|
|
__schedstat_add(se->statistics.sum_sleep_runtime, delta);
|
|
|
|
if (tsk) {
|
|
account_scheduler_latency(tsk, delta >> 10, 1);
|
|
trace_sched_stat_sleep(tsk, delta);
|
|
}
|
|
}
|
|
if (block_start) {
|
|
u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
|
|
|
|
if ((s64)delta < 0)
|
|
delta = 0;
|
|
|
|
if (unlikely(delta > schedstat_val(se->statistics.block_max)))
|
|
__schedstat_set(se->statistics.block_max, delta);
|
|
|
|
__schedstat_set(se->statistics.block_start, 0);
|
|
__schedstat_add(se->statistics.sum_sleep_runtime, delta);
|
|
|
|
if (tsk) {
|
|
if (tsk->in_iowait) {
|
|
__schedstat_add(se->statistics.iowait_sum, delta);
|
|
__schedstat_inc(se->statistics.iowait_count);
|
|
trace_sched_stat_iowait(tsk, delta);
|
|
}
|
|
|
|
trace_sched_stat_blocked(tsk, delta);
|
|
|
|
/*
|
|
* Blocking time is in units of nanosecs, so shift by
|
|
* 20 to get a milliseconds-range estimation of the
|
|
* amount of time that the task spent sleeping:
|
|
*/
|
|
if (unlikely(prof_on == SLEEP_PROFILING)) {
|
|
profile_hits(SLEEP_PROFILING,
|
|
(void *)get_wchan(tsk),
|
|
delta >> 20);
|
|
}
|
|
account_scheduler_latency(tsk, delta >> 10, 0);
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Task is being enqueued - update stats:
|
|
*/
|
|
static inline void
|
|
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
|
|
{
|
|
if (!schedstat_enabled())
|
|
return;
|
|
|
|
/*
|
|
* Are we enqueueing a waiting task? (for current tasks
|
|
* a dequeue/enqueue event is a NOP)
|
|
*/
|
|
if (se != cfs_rq->curr)
|
|
update_stats_wait_start(cfs_rq, se);
|
|
|
|
if (flags & ENQUEUE_WAKEUP)
|
|
update_stats_enqueue_sleeper(cfs_rq, se);
|
|
}
|
|
|
|
static inline void
|
|
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
|
|
{
|
|
|
|
if (!schedstat_enabled())
|
|
return;
|
|
|
|
/*
|
|
* Mark the end of the wait period if dequeueing a
|
|
* waiting task:
|
|
*/
|
|
if (se != cfs_rq->curr)
|
|
update_stats_wait_end(cfs_rq, se);
|
|
|
|
if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
|
|
struct task_struct *tsk = task_of(se);
|
|
|
|
if (tsk->state & TASK_INTERRUPTIBLE)
|
|
__schedstat_set(se->statistics.sleep_start,
|
|
rq_clock(rq_of(cfs_rq)));
|
|
if (tsk->state & TASK_UNINTERRUPTIBLE)
|
|
__schedstat_set(se->statistics.block_start,
|
|
rq_clock(rq_of(cfs_rq)));
|
|
}
|
|
}
|
|
|
|
/*
|
|
* We are picking a new current task - update its stats:
|
|
*/
|
|
static inline void
|
|
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/*
|
|
* We are starting a new run period:
|
|
*/
|
|
se->exec_start = rq_clock_task(rq_of(cfs_rq));
|
|
}
|
|
|
|
/**************************************************
|
|
* Scheduling class queueing methods:
|
|
*/
|
|
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
/*
|
|
* Approximate time to scan a full NUMA task in ms. The task scan period is
|
|
* calculated based on the tasks virtual memory size and
|
|
* numa_balancing_scan_size.
|
|
*/
|
|
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
|
|
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
|
|
|
|
/* Portion of address space to scan in MB */
|
|
unsigned int sysctl_numa_balancing_scan_size = 256;
|
|
|
|
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
|
|
unsigned int sysctl_numa_balancing_scan_delay = 1000;
|
|
|
|
struct numa_group {
|
|
refcount_t refcount;
|
|
|
|
spinlock_t lock; /* nr_tasks, tasks */
|
|
int nr_tasks;
|
|
pid_t gid;
|
|
int active_nodes;
|
|
|
|
struct rcu_head rcu;
|
|
unsigned long total_faults;
|
|
unsigned long max_faults_cpu;
|
|
/*
|
|
* Faults_cpu is used to decide whether memory should move
|
|
* towards the CPU. As a consequence, these stats are weighted
|
|
* more by CPU use than by memory faults.
|
|
*/
|
|
unsigned long *faults_cpu;
|
|
unsigned long faults[0];
|
|
};
|
|
|
|
static inline unsigned long group_faults_priv(struct numa_group *ng);
|
|
static inline unsigned long group_faults_shared(struct numa_group *ng);
|
|
|
|
static unsigned int task_nr_scan_windows(struct task_struct *p)
|
|
{
|
|
unsigned long rss = 0;
|
|
unsigned long nr_scan_pages;
|
|
|
|
/*
|
|
* Calculations based on RSS as non-present and empty pages are skipped
|
|
* by the PTE scanner and NUMA hinting faults should be trapped based
|
|
* on resident pages
|
|
*/
|
|
nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
|
|
rss = get_mm_rss(p->mm);
|
|
if (!rss)
|
|
rss = nr_scan_pages;
|
|
|
|
rss = round_up(rss, nr_scan_pages);
|
|
return rss / nr_scan_pages;
|
|
}
|
|
|
|
/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
|
|
#define MAX_SCAN_WINDOW 2560
|
|
|
|
static unsigned int task_scan_min(struct task_struct *p)
|
|
{
|
|
unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
|
|
unsigned int scan, floor;
|
|
unsigned int windows = 1;
|
|
|
|
if (scan_size < MAX_SCAN_WINDOW)
|
|
windows = MAX_SCAN_WINDOW / scan_size;
|
|
floor = 1000 / windows;
|
|
|
|
scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
|
|
return max_t(unsigned int, floor, scan);
|
|
}
|
|
|
|
static unsigned int task_scan_start(struct task_struct *p)
|
|
{
|
|
unsigned long smin = task_scan_min(p);
|
|
unsigned long period = smin;
|
|
|
|
/* Scale the maximum scan period with the amount of shared memory. */
|
|
if (p->numa_group) {
|
|
struct numa_group *ng = p->numa_group;
|
|
unsigned long shared = group_faults_shared(ng);
|
|
unsigned long private = group_faults_priv(ng);
|
|
|
|
period *= refcount_read(&ng->refcount);
|
|
period *= shared + 1;
|
|
period /= private + shared + 1;
|
|
}
|
|
|
|
return max(smin, period);
|
|
}
|
|
|
|
static unsigned int task_scan_max(struct task_struct *p)
|
|
{
|
|
unsigned long smin = task_scan_min(p);
|
|
unsigned long smax;
|
|
|
|
/* Watch for min being lower than max due to floor calculations */
|
|
smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
|
|
|
|
/* Scale the maximum scan period with the amount of shared memory. */
|
|
if (p->numa_group) {
|
|
struct numa_group *ng = p->numa_group;
|
|
unsigned long shared = group_faults_shared(ng);
|
|
unsigned long private = group_faults_priv(ng);
|
|
unsigned long period = smax;
|
|
|
|
period *= refcount_read(&ng->refcount);
|
|
period *= shared + 1;
|
|
period /= private + shared + 1;
|
|
|
|
smax = max(smax, period);
|
|
}
|
|
|
|
return max(smin, smax);
|
|
}
|
|
|
|
void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
|
|
{
|
|
int mm_users = 0;
|
|
struct mm_struct *mm = p->mm;
|
|
|
|
if (mm) {
|
|
mm_users = atomic_read(&mm->mm_users);
|
|
if (mm_users == 1) {
|
|
mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
|
|
mm->numa_scan_seq = 0;
|
|
}
|
|
}
|
|
p->node_stamp = 0;
|
|
p->numa_scan_seq = mm ? mm->numa_scan_seq : 0;
|
|
p->numa_scan_period = sysctl_numa_balancing_scan_delay;
|
|
p->numa_work.next = &p->numa_work;
|
|
p->numa_faults = NULL;
|
|
p->numa_group = NULL;
|
|
p->last_task_numa_placement = 0;
|
|
p->last_sum_exec_runtime = 0;
|
|
|
|
/* New address space, reset the preferred nid */
|
|
if (!(clone_flags & CLONE_VM)) {
|
|
p->numa_preferred_nid = NUMA_NO_NODE;
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* New thread, keep existing numa_preferred_nid which should be copied
|
|
* already by arch_dup_task_struct but stagger when scans start.
|
|
*/
|
|
if (mm) {
|
|
unsigned int delay;
|
|
|
|
delay = min_t(unsigned int, task_scan_max(current),
|
|
current->numa_scan_period * mm_users * NSEC_PER_MSEC);
|
|
delay += 2 * TICK_NSEC;
|
|
p->node_stamp = delay;
|
|
}
|
|
}
|
|
|
|
static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
|
|
{
|
|
rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE);
|
|
rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
|
|
}
|
|
|
|
static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
|
|
{
|
|
rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE);
|
|
rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
|
|
}
|
|
|
|
/* Shared or private faults. */
|
|
#define NR_NUMA_HINT_FAULT_TYPES 2
|
|
|
|
/* Memory and CPU locality */
|
|
#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
|
|
|
|
/* Averaged statistics, and temporary buffers. */
|
|
#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
|
|
|
|
pid_t task_numa_group_id(struct task_struct *p)
|
|
{
|
|
return p->numa_group ? p->numa_group->gid : 0;
|
|
}
|
|
|
|
/*
|
|
* The averaged statistics, shared & private, memory & CPU,
|
|
* occupy the first half of the array. The second half of the
|
|
* array is for current counters, which are averaged into the
|
|
* first set by task_numa_placement.
|
|
*/
|
|
static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
|
|
{
|
|
return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
|
|
}
|
|
|
|
static inline unsigned long task_faults(struct task_struct *p, int nid)
|
|
{
|
|
if (!p->numa_faults)
|
|
return 0;
|
|
|
|
return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
|
|
p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
|
|
}
|
|
|
|
static inline unsigned long group_faults(struct task_struct *p, int nid)
|
|
{
|
|
if (!p->numa_group)
|
|
return 0;
|
|
|
|
return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
|
|
p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
|
|
}
|
|
|
|
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
|
|
{
|
|
return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
|
|
group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
|
|
}
|
|
|
|
static inline unsigned long group_faults_priv(struct numa_group *ng)
|
|
{
|
|
unsigned long faults = 0;
|
|
int node;
|
|
|
|
for_each_online_node(node) {
|
|
faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
|
|
}
|
|
|
|
return faults;
|
|
}
|
|
|
|
static inline unsigned long group_faults_shared(struct numa_group *ng)
|
|
{
|
|
unsigned long faults = 0;
|
|
int node;
|
|
|
|
for_each_online_node(node) {
|
|
faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
|
|
}
|
|
|
|
return faults;
|
|
}
|
|
|
|
/*
|
|
* A node triggering more than 1/3 as many NUMA faults as the maximum is
|
|
* considered part of a numa group's pseudo-interleaving set. Migrations
|
|
* between these nodes are slowed down, to allow things to settle down.
|
|
*/
|
|
#define ACTIVE_NODE_FRACTION 3
|
|
|
|
static bool numa_is_active_node(int nid, struct numa_group *ng)
|
|
{
|
|
return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
|
|
}
|
|
|
|
/* Handle placement on systems where not all nodes are directly connected. */
|
|
static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
|
|
int maxdist, bool task)
|
|
{
|
|
unsigned long score = 0;
|
|
int node;
|
|
|
|
/*
|
|
* All nodes are directly connected, and the same distance
|
|
* from each other. No need for fancy placement algorithms.
|
|
*/
|
|
if (sched_numa_topology_type == NUMA_DIRECT)
|
|
return 0;
|
|
|
|
/*
|
|
* This code is called for each node, introducing N^2 complexity,
|
|
* which should be ok given the number of nodes rarely exceeds 8.
|
|
*/
|
|
for_each_online_node(node) {
|
|
unsigned long faults;
|
|
int dist = node_distance(nid, node);
|
|
|
|
/*
|
|
* The furthest away nodes in the system are not interesting
|
|
* for placement; nid was already counted.
|
|
*/
|
|
if (dist == sched_max_numa_distance || node == nid)
|
|
continue;
|
|
|
|
/*
|
|
* On systems with a backplane NUMA topology, compare groups
|
|
* of nodes, and move tasks towards the group with the most
|
|
* memory accesses. When comparing two nodes at distance
|
|
* "hoplimit", only nodes closer by than "hoplimit" are part
|
|
* of each group. Skip other nodes.
|
|
*/
|
|
if (sched_numa_topology_type == NUMA_BACKPLANE &&
|
|
dist >= maxdist)
|
|
continue;
|
|
|
|
/* Add up the faults from nearby nodes. */
|
|
if (task)
|
|
faults = task_faults(p, node);
|
|
else
|
|
faults = group_faults(p, node);
|
|
|
|
/*
|
|
* On systems with a glueless mesh NUMA topology, there are
|
|
* no fixed "groups of nodes". Instead, nodes that are not
|
|
* directly connected bounce traffic through intermediate
|
|
* nodes; a numa_group can occupy any set of nodes.
|
|
* The further away a node is, the less the faults count.
|
|
* This seems to result in good task placement.
|
|
*/
|
|
if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
|
|
faults *= (sched_max_numa_distance - dist);
|
|
faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
|
|
}
|
|
|
|
score += faults;
|
|
}
|
|
|
|
return score;
|
|
}
|
|
|
|
/*
|
|
* These return the fraction of accesses done by a particular task, or
|
|
* task group, on a particular numa node. The group weight is given a
|
|
* larger multiplier, in order to group tasks together that are almost
|
|
* evenly spread out between numa nodes.
|
|
*/
|
|
static inline unsigned long task_weight(struct task_struct *p, int nid,
|
|
int dist)
|
|
{
|
|
unsigned long faults, total_faults;
|
|
|
|
if (!p->numa_faults)
|
|
return 0;
|
|
|
|
total_faults = p->total_numa_faults;
|
|
|
|
if (!total_faults)
|
|
return 0;
|
|
|
|
faults = task_faults(p, nid);
|
|
faults += score_nearby_nodes(p, nid, dist, true);
|
|
|
|
return 1000 * faults / total_faults;
|
|
}
|
|
|
|
static inline unsigned long group_weight(struct task_struct *p, int nid,
|
|
int dist)
|
|
{
|
|
unsigned long faults, total_faults;
|
|
|
|
if (!p->numa_group)
|
|
return 0;
|
|
|
|
total_faults = p->numa_group->total_faults;
|
|
|
|
if (!total_faults)
|
|
return 0;
|
|
|
|
faults = group_faults(p, nid);
|
|
faults += score_nearby_nodes(p, nid, dist, false);
|
|
|
|
return 1000 * faults / total_faults;
|
|
}
|
|
|
|
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
|
|
int src_nid, int dst_cpu)
|
|
{
|
|
struct numa_group *ng = p->numa_group;
|
|
int dst_nid = cpu_to_node(dst_cpu);
|
|
int last_cpupid, this_cpupid;
|
|
|
|
this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
|
|
last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
|
|
|
|
/*
|
|
* Allow first faults or private faults to migrate immediately early in
|
|
* the lifetime of a task. The magic number 4 is based on waiting for
|
|
* two full passes of the "multi-stage node selection" test that is
|
|
* executed below.
|
|
*/
|
|
if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= 4) &&
|
|
(cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid)))
|
|
return true;
|
|
|
|
/*
|
|
* Multi-stage node selection is used in conjunction with a periodic
|
|
* migration fault to build a temporal task<->page relation. By using
|
|
* a two-stage filter we remove short/unlikely relations.
|
|
*
|
|
* Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
|
|
* a task's usage of a particular page (n_p) per total usage of this
|
|
* page (n_t) (in a given time-span) to a probability.
|
|
*
|
|
* Our periodic faults will sample this probability and getting the
|
|
* same result twice in a row, given these samples are fully
|
|
* independent, is then given by P(n)^2, provided our sample period
|
|
* is sufficiently short compared to the usage pattern.
|
|
*
|
|
* This quadric squishes small probabilities, making it less likely we
|
|
* act on an unlikely task<->page relation.
|
|
*/
|
|
if (!cpupid_pid_unset(last_cpupid) &&
|
|
cpupid_to_nid(last_cpupid) != dst_nid)
|
|
return false;
|
|
|
|
/* Always allow migrate on private faults */
|
|
if (cpupid_match_pid(p, last_cpupid))
|
|
return true;
|
|
|
|
/* A shared fault, but p->numa_group has not been set up yet. */
|
|
if (!ng)
|
|
return true;
|
|
|
|
/*
|
|
* Destination node is much more heavily used than the source
|
|
* node? Allow migration.
|
|
*/
|
|
if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
|
|
ACTIVE_NODE_FRACTION)
|
|
return true;
|
|
|
|
/*
|
|
* Distribute memory according to CPU & memory use on each node,
|
|
* with 3/4 hysteresis to avoid unnecessary memory migrations:
|
|
*
|
|
* faults_cpu(dst) 3 faults_cpu(src)
|
|
* --------------- * - > ---------------
|
|
* faults_mem(dst) 4 faults_mem(src)
|
|
*/
|
|
return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
|
|
group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
|
|
}
|
|
|
|
static unsigned long weighted_cpuload(struct rq *rq);
|
|
static unsigned long source_load(int cpu, int type);
|
|
static unsigned long target_load(int cpu, int type);
|
|
|
|
/* Cached statistics for all CPUs within a node */
|
|
struct numa_stats {
|
|
unsigned long load;
|
|
|
|
/* Total compute capacity of CPUs on a node */
|
|
unsigned long compute_capacity;
|
|
};
|
|
|
|
/*
|
|
* XXX borrowed from update_sg_lb_stats
|
|
*/
|
|
static void update_numa_stats(struct numa_stats *ns, int nid)
|
|
{
|
|
int cpu;
|
|
|
|
memset(ns, 0, sizeof(*ns));
|
|
for_each_cpu(cpu, cpumask_of_node(nid)) {
|
|
struct rq *rq = cpu_rq(cpu);
|
|
|
|
ns->load += weighted_cpuload(rq);
|
|
ns->compute_capacity += capacity_of(cpu);
|
|
}
|
|
|
|
}
|
|
|
|
struct task_numa_env {
|
|
struct task_struct *p;
|
|
|
|
int src_cpu, src_nid;
|
|
int dst_cpu, dst_nid;
|
|
|
|
struct numa_stats src_stats, dst_stats;
|
|
|
|
int imbalance_pct;
|
|
int dist;
|
|
|
|
struct task_struct *best_task;
|
|
long best_imp;
|
|
int best_cpu;
|
|
};
|
|
|
|
static void task_numa_assign(struct task_numa_env *env,
|
|
struct task_struct *p, long imp)
|
|
{
|
|
struct rq *rq = cpu_rq(env->dst_cpu);
|
|
|
|
/* Bail out if run-queue part of active NUMA balance. */
|
|
if (xchg(&rq->numa_migrate_on, 1))
|
|
return;
|
|
|
|
/*
|
|
* Clear previous best_cpu/rq numa-migrate flag, since task now
|
|
* found a better CPU to move/swap.
|
|
*/
|
|
if (env->best_cpu != -1) {
|
|
rq = cpu_rq(env->best_cpu);
|
|
WRITE_ONCE(rq->numa_migrate_on, 0);
|
|
}
|
|
|
|
if (env->best_task)
|
|
put_task_struct(env->best_task);
|
|
if (p)
|
|
get_task_struct(p);
|
|
|
|
env->best_task = p;
|
|
env->best_imp = imp;
|
|
env->best_cpu = env->dst_cpu;
|
|
}
|
|
|
|
static bool load_too_imbalanced(long src_load, long dst_load,
|
|
struct task_numa_env *env)
|
|
{
|
|
long imb, old_imb;
|
|
long orig_src_load, orig_dst_load;
|
|
long src_capacity, dst_capacity;
|
|
|
|
/*
|
|
* The load is corrected for the CPU capacity available on each node.
|
|
*
|
|
* src_load dst_load
|
|
* ------------ vs ---------
|
|
* src_capacity dst_capacity
|
|
*/
|
|
src_capacity = env->src_stats.compute_capacity;
|
|
dst_capacity = env->dst_stats.compute_capacity;
|
|
|
|
imb = abs(dst_load * src_capacity - src_load * dst_capacity);
|
|
|
|
orig_src_load = env->src_stats.load;
|
|
orig_dst_load = env->dst_stats.load;
|
|
|
|
old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
|
|
|
|
/* Would this change make things worse? */
|
|
return (imb > old_imb);
|
|
}
|
|
|
|
/*
|
|
* Maximum NUMA importance can be 1998 (2*999);
|
|
* SMALLIMP @ 30 would be close to 1998/64.
|
|
* Used to deter task migration.
|
|
*/
|
|
#define SMALLIMP 30
|
|
|
|
/*
|
|
* This checks if the overall compute and NUMA accesses of the system would
|
|
* be improved if the source tasks was migrated to the target dst_cpu taking
|
|
* into account that it might be best if task running on the dst_cpu should
|
|
* be exchanged with the source task
|
|
*/
|
|
static void task_numa_compare(struct task_numa_env *env,
|
|
long taskimp, long groupimp, bool maymove)
|
|
{
|
|
struct rq *dst_rq = cpu_rq(env->dst_cpu);
|
|
struct task_struct *cur;
|
|
long src_load, dst_load;
|
|
long load;
|
|
long imp = env->p->numa_group ? groupimp : taskimp;
|
|
long moveimp = imp;
|
|
int dist = env->dist;
|
|
|
|
if (READ_ONCE(dst_rq->numa_migrate_on))
|
|
return;
|
|
|
|
rcu_read_lock();
|
|
cur = task_rcu_dereference(&dst_rq->curr);
|
|
if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
|
|
cur = NULL;
|
|
|
|
/*
|
|
* Because we have preemption enabled we can get migrated around and
|
|
* end try selecting ourselves (current == env->p) as a swap candidate.
|
|
*/
|
|
if (cur == env->p)
|
|
goto unlock;
|
|
|
|
if (!cur) {
|
|
if (maymove && moveimp >= env->best_imp)
|
|
goto assign;
|
|
else
|
|
goto unlock;
|
|
}
|
|
|
|
/*
|
|
* "imp" is the fault differential for the source task between the
|
|
* source and destination node. Calculate the total differential for
|
|
* the source task and potential destination task. The more negative
|
|
* the value is, the more remote accesses that would be expected to
|
|
* be incurred if the tasks were swapped.
|
|
*/
|
|
/* Skip this swap candidate if cannot move to the source cpu */
|
|
if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
|
|
goto unlock;
|
|
|
|
/*
|
|
* If dst and source tasks are in the same NUMA group, or not
|
|
* in any group then look only at task weights.
|
|
*/
|
|
if (cur->numa_group == env->p->numa_group) {
|
|
imp = taskimp + task_weight(cur, env->src_nid, dist) -
|
|
task_weight(cur, env->dst_nid, dist);
|
|
/*
|
|
* Add some hysteresis to prevent swapping the
|
|
* tasks within a group over tiny differences.
|
|
*/
|
|
if (cur->numa_group)
|
|
imp -= imp / 16;
|
|
} else {
|
|
/*
|
|
* Compare the group weights. If a task is all by itself
|
|
* (not part of a group), use the task weight instead.
|
|
*/
|
|
if (cur->numa_group && env->p->numa_group)
|
|
imp += group_weight(cur, env->src_nid, dist) -
|
|
group_weight(cur, env->dst_nid, dist);
|
|
else
|
|
imp += task_weight(cur, env->src_nid, dist) -
|
|
task_weight(cur, env->dst_nid, dist);
|
|
}
|
|
|
|
if (maymove && moveimp > imp && moveimp > env->best_imp) {
|
|
imp = moveimp;
|
|
cur = NULL;
|
|
goto assign;
|
|
}
|
|
|
|
/*
|
|
* If the NUMA importance is less than SMALLIMP,
|
|
* task migration might only result in ping pong
|
|
* of tasks and also hurt performance due to cache
|
|
* misses.
|
|
*/
|
|
if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
|
|
goto unlock;
|
|
|
|
/*
|
|
* In the overloaded case, try and keep the load balanced.
|
|
*/
|
|
load = task_h_load(env->p) - task_h_load(cur);
|
|
if (!load)
|
|
goto assign;
|
|
|
|
dst_load = env->dst_stats.load + load;
|
|
src_load = env->src_stats.load - load;
|
|
|
|
if (load_too_imbalanced(src_load, dst_load, env))
|
|
goto unlock;
|
|
|
|
assign:
|
|
/*
|
|
* One idle CPU per node is evaluated for a task numa move.
|
|
* Call select_idle_sibling to maybe find a better one.
|
|
*/
|
|
if (!cur) {
|
|
/*
|
|
* select_idle_siblings() uses an per-CPU cpumask that
|
|
* can be used from IRQ context.
|
|
*/
|
|
local_irq_disable();
|
|
env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
|
|
env->dst_cpu);
|
|
local_irq_enable();
|
|
}
|
|
|
|
task_numa_assign(env, cur, imp);
|
|
unlock:
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
static void task_numa_find_cpu(struct task_numa_env *env,
|
|
long taskimp, long groupimp)
|
|
{
|
|
long src_load, dst_load, load;
|
|
bool maymove = false;
|
|
int cpu;
|
|
|
|
load = task_h_load(env->p);
|
|
dst_load = env->dst_stats.load + load;
|
|
src_load = env->src_stats.load - load;
|
|
|
|
/*
|
|
* If the improvement from just moving env->p direction is better
|
|
* than swapping tasks around, check if a move is possible.
|
|
*/
|
|
maymove = !load_too_imbalanced(src_load, dst_load, env);
|
|
|
|
for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
|
|
/* Skip this CPU if the source task cannot migrate */
|
|
if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
|
|
continue;
|
|
|
|
env->dst_cpu = cpu;
|
|
task_numa_compare(env, taskimp, groupimp, maymove);
|
|
}
|
|
}
|
|
|
|
static int task_numa_migrate(struct task_struct *p)
|
|
{
|
|
struct task_numa_env env = {
|
|
.p = p,
|
|
|
|
.src_cpu = task_cpu(p),
|
|
.src_nid = task_node(p),
|
|
|
|
.imbalance_pct = 112,
|
|
|
|
.best_task = NULL,
|
|
.best_imp = 0,
|
|
.best_cpu = -1,
|
|
};
|
|
struct sched_domain *sd;
|
|
struct rq *best_rq;
|
|
unsigned long taskweight, groupweight;
|
|
int nid, ret, dist;
|
|
long taskimp, groupimp;
|
|
|
|
/*
|
|
* Pick the lowest SD_NUMA domain, as that would have the smallest
|
|
* imbalance and would be the first to start moving tasks about.
|
|
*
|
|
* And we want to avoid any moving of tasks about, as that would create
|
|
* random movement of tasks -- counter the numa conditions we're trying
|
|
* to satisfy here.
|
|
*/
|
|
rcu_read_lock();
|
|
sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
|
|
if (sd)
|
|
env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* Cpusets can break the scheduler domain tree into smaller
|
|
* balance domains, some of which do not cross NUMA boundaries.
|
|
* Tasks that are "trapped" in such domains cannot be migrated
|
|
* elsewhere, so there is no point in (re)trying.
|
|
*/
|
|
if (unlikely(!sd)) {
|
|
sched_setnuma(p, task_node(p));
|
|
return -EINVAL;
|
|
}
|
|
|
|
env.dst_nid = p->numa_preferred_nid;
|
|
dist = env.dist = node_distance(env.src_nid, env.dst_nid);
|
|
taskweight = task_weight(p, env.src_nid, dist);
|
|
groupweight = group_weight(p, env.src_nid, dist);
|
|
update_numa_stats(&env.src_stats, env.src_nid);
|
|
taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
|
|
groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
|
|
update_numa_stats(&env.dst_stats, env.dst_nid);
|
|
|
|
/* Try to find a spot on the preferred nid. */
|
|
task_numa_find_cpu(&env, taskimp, groupimp);
|
|
|
|
/*
|
|
* Look at other nodes in these cases:
|
|
* - there is no space available on the preferred_nid
|
|
* - the task is part of a numa_group that is interleaved across
|
|
* multiple NUMA nodes; in order to better consolidate the group,
|
|
* we need to check other locations.
|
|
*/
|
|
if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
|
|
for_each_online_node(nid) {
|
|
if (nid == env.src_nid || nid == p->numa_preferred_nid)
|
|
continue;
|
|
|
|
dist = node_distance(env.src_nid, env.dst_nid);
|
|
if (sched_numa_topology_type == NUMA_BACKPLANE &&
|
|
dist != env.dist) {
|
|
taskweight = task_weight(p, env.src_nid, dist);
|
|
groupweight = group_weight(p, env.src_nid, dist);
|
|
}
|
|
|
|
/* Only consider nodes where both task and groups benefit */
|
|
taskimp = task_weight(p, nid, dist) - taskweight;
|
|
groupimp = group_weight(p, nid, dist) - groupweight;
|
|
if (taskimp < 0 && groupimp < 0)
|
|
continue;
|
|
|
|
env.dist = dist;
|
|
env.dst_nid = nid;
|
|
update_numa_stats(&env.dst_stats, env.dst_nid);
|
|
task_numa_find_cpu(&env, taskimp, groupimp);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the task is part of a workload that spans multiple NUMA nodes,
|
|
* and is migrating into one of the workload's active nodes, remember
|
|
* this node as the task's preferred numa node, so the workload can
|
|
* settle down.
|
|
* A task that migrated to a second choice node will be better off
|
|
* trying for a better one later. Do not set the preferred node here.
|
|
*/
|
|
if (p->numa_group) {
|
|
if (env.best_cpu == -1)
|
|
nid = env.src_nid;
|
|
else
|
|
nid = cpu_to_node(env.best_cpu);
|
|
|
|
if (nid != p->numa_preferred_nid)
|
|
sched_setnuma(p, nid);
|
|
}
|
|
|
|
/* No better CPU than the current one was found. */
|
|
if (env.best_cpu == -1)
|
|
return -EAGAIN;
|
|
|
|
best_rq = cpu_rq(env.best_cpu);
|
|
if (env.best_task == NULL) {
|
|
ret = migrate_task_to(p, env.best_cpu);
|
|
WRITE_ONCE(best_rq->numa_migrate_on, 0);
|
|
if (ret != 0)
|
|
trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
|
|
return ret;
|
|
}
|
|
|
|
ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
|
|
WRITE_ONCE(best_rq->numa_migrate_on, 0);
|
|
|
|
if (ret != 0)
|
|
trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
|
|
put_task_struct(env.best_task);
|
|
return ret;
|
|
}
|
|
|
|
/* Attempt to migrate a task to a CPU on the preferred node. */
|
|
static void numa_migrate_preferred(struct task_struct *p)
|
|
{
|
|
unsigned long interval = HZ;
|
|
|
|
/* This task has no NUMA fault statistics yet */
|
|
if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults))
|
|
return;
|
|
|
|
/* Periodically retry migrating the task to the preferred node */
|
|
interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
|
|
p->numa_migrate_retry = jiffies + interval;
|
|
|
|
/* Success if task is already running on preferred CPU */
|
|
if (task_node(p) == p->numa_preferred_nid)
|
|
return;
|
|
|
|
/* Otherwise, try migrate to a CPU on the preferred node */
|
|
task_numa_migrate(p);
|
|
}
|
|
|
|
/*
|
|
* Find out how many nodes on the workload is actively running on. Do this by
|
|
* tracking the nodes from which NUMA hinting faults are triggered. This can
|
|
* be different from the set of nodes where the workload's memory is currently
|
|
* located.
|
|
*/
|
|
static void numa_group_count_active_nodes(struct numa_group *numa_group)
|
|
{
|
|
unsigned long faults, max_faults = 0;
|
|
int nid, active_nodes = 0;
|
|
|
|
for_each_online_node(nid) {
|
|
faults = group_faults_cpu(numa_group, nid);
|
|
if (faults > max_faults)
|
|
max_faults = faults;
|
|
}
|
|
|
|
for_each_online_node(nid) {
|
|
faults = group_faults_cpu(numa_group, nid);
|
|
if (faults * ACTIVE_NODE_FRACTION > max_faults)
|
|
active_nodes++;
|
|
}
|
|
|
|
numa_group->max_faults_cpu = max_faults;
|
|
numa_group->active_nodes = active_nodes;
|
|
}
|
|
|
|
/*
|
|
* When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
|
|
* increments. The more local the fault statistics are, the higher the scan
|
|
* period will be for the next scan window. If local/(local+remote) ratio is
|
|
* below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
|
|
* the scan period will decrease. Aim for 70% local accesses.
|
|
*/
|
|
#define NUMA_PERIOD_SLOTS 10
|
|
#define NUMA_PERIOD_THRESHOLD 7
|
|
|
|
/*
|
|
* Increase the scan period (slow down scanning) if the majority of
|
|
* our memory is already on our local node, or if the majority of
|
|
* the page accesses are shared with other processes.
|
|
* Otherwise, decrease the scan period.
|
|
*/
|
|
static void update_task_scan_period(struct task_struct *p,
|
|
unsigned long shared, unsigned long private)
|
|
{
|
|
unsigned int period_slot;
|
|
int lr_ratio, ps_ratio;
|
|
int diff;
|
|
|
|
unsigned long remote = p->numa_faults_locality[0];
|
|
unsigned long local = p->numa_faults_locality[1];
|
|
|
|
/*
|
|
* If there were no record hinting faults then either the task is
|
|
* completely idle or all activity is areas that are not of interest
|
|
* to automatic numa balancing. Related to that, if there were failed
|
|
* migration then it implies we are migrating too quickly or the local
|
|
* node is overloaded. In either case, scan slower
|
|
*/
|
|
if (local + shared == 0 || p->numa_faults_locality[2]) {
|
|
p->numa_scan_period = min(p->numa_scan_period_max,
|
|
p->numa_scan_period << 1);
|
|
|
|
p->mm->numa_next_scan = jiffies +
|
|
msecs_to_jiffies(p->numa_scan_period);
|
|
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Prepare to scale scan period relative to the current period.
|
|
* == NUMA_PERIOD_THRESHOLD scan period stays the same
|
|
* < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
|
|
* >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
|
|
*/
|
|
period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
|
|
lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
|
|
ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
|
|
|
|
if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
|
|
/*
|
|
* Most memory accesses are local. There is no need to
|
|
* do fast NUMA scanning, since memory is already local.
|
|
*/
|
|
int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
|
|
if (!slot)
|
|
slot = 1;
|
|
diff = slot * period_slot;
|
|
} else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
|
|
/*
|
|
* Most memory accesses are shared with other tasks.
|
|
* There is no point in continuing fast NUMA scanning,
|
|
* since other tasks may just move the memory elsewhere.
|
|
*/
|
|
int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
|
|
if (!slot)
|
|
slot = 1;
|
|
diff = slot * period_slot;
|
|
} else {
|
|
/*
|
|
* Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
|
|
* yet they are not on the local NUMA node. Speed up
|
|
* NUMA scanning to get the memory moved over.
|
|
*/
|
|
int ratio = max(lr_ratio, ps_ratio);
|
|
diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
|
|
}
|
|
|
|
p->numa_scan_period = clamp(p->numa_scan_period + diff,
|
|
task_scan_min(p), task_scan_max(p));
|
|
memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
|
|
}
|
|
|
|
/*
|
|
* Get the fraction of time the task has been running since the last
|
|
* NUMA placement cycle. The scheduler keeps similar statistics, but
|
|
* decays those on a 32ms period, which is orders of magnitude off
|
|
* from the dozens-of-seconds NUMA balancing period. Use the scheduler
|
|
* stats only if the task is so new there are no NUMA statistics yet.
|
|
*/
|
|
static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
|
|
{
|
|
u64 runtime, delta, now;
|
|
/* Use the start of this time slice to avoid calculations. */
|
|
now = p->se.exec_start;
|
|
runtime = p->se.sum_exec_runtime;
|
|
|
|
if (p->last_task_numa_placement) {
|
|
delta = runtime - p->last_sum_exec_runtime;
|
|
*period = now - p->last_task_numa_placement;
|
|
} else {
|
|
delta = p->se.avg.load_sum;
|
|
*period = LOAD_AVG_MAX;
|
|
}
|
|
|
|
p->last_sum_exec_runtime = runtime;
|
|
p->last_task_numa_placement = now;
|
|
|
|
return delta;
|
|
}
|
|
|
|
/*
|
|
* Determine the preferred nid for a task in a numa_group. This needs to
|
|
* be done in a way that produces consistent results with group_weight,
|
|
* otherwise workloads might not converge.
|
|
*/
|
|
static int preferred_group_nid(struct task_struct *p, int nid)
|
|
{
|
|
nodemask_t nodes;
|
|
int dist;
|
|
|
|
/* Direct connections between all NUMA nodes. */
|
|
if (sched_numa_topology_type == NUMA_DIRECT)
|
|
return nid;
|
|
|
|
/*
|
|
* On a system with glueless mesh NUMA topology, group_weight
|
|
* scores nodes according to the number of NUMA hinting faults on
|
|
* both the node itself, and on nearby nodes.
|
|
*/
|
|
if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
|
|
unsigned long score, max_score = 0;
|
|
int node, max_node = nid;
|
|
|
|
dist = sched_max_numa_distance;
|
|
|
|
for_each_online_node(node) {
|
|
score = group_weight(p, node, dist);
|
|
if (score > max_score) {
|
|
max_score = score;
|
|
max_node = node;
|
|
}
|
|
}
|
|
return max_node;
|
|
}
|
|
|
|
/*
|
|
* Finding the preferred nid in a system with NUMA backplane
|
|
* interconnect topology is more involved. The goal is to locate
|
|
* tasks from numa_groups near each other in the system, and
|
|
* untangle workloads from different sides of the system. This requires
|
|
* searching down the hierarchy of node groups, recursively searching
|
|
* inside the highest scoring group of nodes. The nodemask tricks
|
|
* keep the complexity of the search down.
|
|
*/
|
|
nodes = node_online_map;
|
|
for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
|
|
unsigned long max_faults = 0;
|
|
nodemask_t max_group = NODE_MASK_NONE;
|
|
int a, b;
|
|
|
|
/* Are there nodes at this distance from each other? */
|
|
if (!find_numa_distance(dist))
|
|
continue;
|
|
|
|
for_each_node_mask(a, nodes) {
|
|
unsigned long faults = 0;
|
|
nodemask_t this_group;
|
|
nodes_clear(this_group);
|
|
|
|
/* Sum group's NUMA faults; includes a==b case. */
|
|
for_each_node_mask(b, nodes) {
|
|
if (node_distance(a, b) < dist) {
|
|
faults += group_faults(p, b);
|
|
node_set(b, this_group);
|
|
node_clear(b, nodes);
|
|
}
|
|
}
|
|
|
|
/* Remember the top group. */
|
|
if (faults > max_faults) {
|
|
max_faults = faults;
|
|
max_group = this_group;
|
|
/*
|
|
* subtle: at the smallest distance there is
|
|
* just one node left in each "group", the
|
|
* winner is the preferred nid.
|
|
*/
|
|
nid = a;
|
|
}
|
|
}
|
|
/* Next round, evaluate the nodes within max_group. */
|
|
if (!max_faults)
|
|
break;
|
|
nodes = max_group;
|
|
}
|
|
return nid;
|
|
}
|
|
|
|
static void task_numa_placement(struct task_struct *p)
|
|
{
|
|
int seq, nid, max_nid = NUMA_NO_NODE;
|
|
unsigned long max_faults = 0;
|
|
unsigned long fault_types[2] = { 0, 0 };
|
|
unsigned long total_faults;
|
|
u64 runtime, period;
|
|
spinlock_t *group_lock = NULL;
|
|
|
|
/*
|
|
* The p->mm->numa_scan_seq field gets updated without
|
|
* exclusive access. Use READ_ONCE() here to ensure
|
|
* that the field is read in a single access:
|
|
*/
|
|
seq = READ_ONCE(p->mm->numa_scan_seq);
|
|
if (p->numa_scan_seq == seq)
|
|
return;
|
|
p->numa_scan_seq = seq;
|
|
p->numa_scan_period_max = task_scan_max(p);
|
|
|
|
total_faults = p->numa_faults_locality[0] +
|
|
p->numa_faults_locality[1];
|
|
runtime = numa_get_avg_runtime(p, &period);
|
|
|
|
/* If the task is part of a group prevent parallel updates to group stats */
|
|
if (p->numa_group) {
|
|
group_lock = &p->numa_group->lock;
|
|
spin_lock_irq(group_lock);
|
|
}
|
|
|
|
/* Find the node with the highest number of faults */
|
|
for_each_online_node(nid) {
|
|
/* Keep track of the offsets in numa_faults array */
|
|
int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
|
|
unsigned long faults = 0, group_faults = 0;
|
|
int priv;
|
|
|
|
for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
|
|
long diff, f_diff, f_weight;
|
|
|
|
mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
|
|
membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
|
|
cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
|
|
cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
|
|
|
|
/* Decay existing window, copy faults since last scan */
|
|
diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
|
|
fault_types[priv] += p->numa_faults[membuf_idx];
|
|
p->numa_faults[membuf_idx] = 0;
|
|
|
|
/*
|
|
* Normalize the faults_from, so all tasks in a group
|
|
* count according to CPU use, instead of by the raw
|
|
* number of faults. Tasks with little runtime have
|
|
* little over-all impact on throughput, and thus their
|
|
* faults are less important.
|
|
*/
|
|
f_weight = div64_u64(runtime << 16, period + 1);
|
|
f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
|
|
(total_faults + 1);
|
|
f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
|
|
p->numa_faults[cpubuf_idx] = 0;
|
|
|
|
p->numa_faults[mem_idx] += diff;
|
|
p->numa_faults[cpu_idx] += f_diff;
|
|
faults += p->numa_faults[mem_idx];
|
|
p->total_numa_faults += diff;
|
|
if (p->numa_group) {
|
|
/*
|
|
* safe because we can only change our own group
|
|
*
|
|
* mem_idx represents the offset for a given
|
|
* nid and priv in a specific region because it
|
|
* is at the beginning of the numa_faults array.
|
|
*/
|
|
p->numa_group->faults[mem_idx] += diff;
|
|
p->numa_group->faults_cpu[mem_idx] += f_diff;
|
|
p->numa_group->total_faults += diff;
|
|
group_faults += p->numa_group->faults[mem_idx];
|
|
}
|
|
}
|
|
|
|
if (!p->numa_group) {
|
|
if (faults > max_faults) {
|
|
max_faults = faults;
|
|
max_nid = nid;
|
|
}
|
|
} else if (group_faults > max_faults) {
|
|
max_faults = group_faults;
|
|
max_nid = nid;
|
|
}
|
|
}
|
|
|
|
if (p->numa_group) {
|
|
numa_group_count_active_nodes(p->numa_group);
|
|
spin_unlock_irq(group_lock);
|
|
max_nid = preferred_group_nid(p, max_nid);
|
|
}
|
|
|
|
if (max_faults) {
|
|
/* Set the new preferred node */
|
|
if (max_nid != p->numa_preferred_nid)
|
|
sched_setnuma(p, max_nid);
|
|
}
|
|
|
|
update_task_scan_period(p, fault_types[0], fault_types[1]);
|
|
}
|
|
|
|
static inline int get_numa_group(struct numa_group *grp)
|
|
{
|
|
return refcount_inc_not_zero(&grp->refcount);
|
|
}
|
|
|
|
static inline void put_numa_group(struct numa_group *grp)
|
|
{
|
|
if (refcount_dec_and_test(&grp->refcount))
|
|
kfree_rcu(grp, rcu);
|
|
}
|
|
|
|
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
|
|
int *priv)
|
|
{
|
|
struct numa_group *grp, *my_grp;
|
|
struct task_struct *tsk;
|
|
bool join = false;
|
|
int cpu = cpupid_to_cpu(cpupid);
|
|
int i;
|
|
|
|
if (unlikely(!p->numa_group)) {
|
|
unsigned int size = sizeof(struct numa_group) +
|
|
4*nr_node_ids*sizeof(unsigned long);
|
|
|
|
grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
|
|
if (!grp)
|
|
return;
|
|
|
|
refcount_set(&grp->refcount, 1);
|
|
grp->active_nodes = 1;
|
|
grp->max_faults_cpu = 0;
|
|
spin_lock_init(&grp->lock);
|
|
grp->gid = p->pid;
|
|
/* Second half of the array tracks nids where faults happen */
|
|
grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
|
|
nr_node_ids;
|
|
|
|
for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
|
|
grp->faults[i] = p->numa_faults[i];
|
|
|
|
grp->total_faults = p->total_numa_faults;
|
|
|
|
grp->nr_tasks++;
|
|
rcu_assign_pointer(p->numa_group, grp);
|
|
}
|
|
|
|
rcu_read_lock();
|
|
tsk = READ_ONCE(cpu_rq(cpu)->curr);
|
|
|
|
if (!cpupid_match_pid(tsk, cpupid))
|
|
goto no_join;
|
|
|
|
grp = rcu_dereference(tsk->numa_group);
|
|
if (!grp)
|
|
goto no_join;
|
|
|
|
my_grp = p->numa_group;
|
|
if (grp == my_grp)
|
|
goto no_join;
|
|
|
|
/*
|
|
* Only join the other group if its bigger; if we're the bigger group,
|
|
* the other task will join us.
|
|
*/
|
|
if (my_grp->nr_tasks > grp->nr_tasks)
|
|
goto no_join;
|
|
|
|
/*
|
|
* Tie-break on the grp address.
|
|
*/
|
|
if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
|
|
goto no_join;
|
|
|
|
/* Always join threads in the same process. */
|
|
if (tsk->mm == current->mm)
|
|
join = true;
|
|
|
|
/* Simple filter to avoid false positives due to PID collisions */
|
|
if (flags & TNF_SHARED)
|
|
join = true;
|
|
|
|
/* Update priv based on whether false sharing was detected */
|
|
*priv = !join;
|
|
|
|
if (join && !get_numa_group(grp))
|
|
goto no_join;
|
|
|
|
rcu_read_unlock();
|
|
|
|
if (!join)
|
|
return;
|
|
|
|
BUG_ON(irqs_disabled());
|
|
double_lock_irq(&my_grp->lock, &grp->lock);
|
|
|
|
for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
|
|
my_grp->faults[i] -= p->numa_faults[i];
|
|
grp->faults[i] += p->numa_faults[i];
|
|
}
|
|
my_grp->total_faults -= p->total_numa_faults;
|
|
grp->total_faults += p->total_numa_faults;
|
|
|
|
my_grp->nr_tasks--;
|
|
grp->nr_tasks++;
|
|
|
|
spin_unlock(&my_grp->lock);
|
|
spin_unlock_irq(&grp->lock);
|
|
|
|
rcu_assign_pointer(p->numa_group, grp);
|
|
|
|
put_numa_group(my_grp);
|
|
return;
|
|
|
|
no_join:
|
|
rcu_read_unlock();
|
|
return;
|
|
}
|
|
|
|
void task_numa_free(struct task_struct *p)
|
|
{
|
|
struct numa_group *grp = p->numa_group;
|
|
void *numa_faults = p->numa_faults;
|
|
unsigned long flags;
|
|
int i;
|
|
|
|
if (grp) {
|
|
spin_lock_irqsave(&grp->lock, flags);
|
|
for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
|
|
grp->faults[i] -= p->numa_faults[i];
|
|
grp->total_faults -= p->total_numa_faults;
|
|
|
|
grp->nr_tasks--;
|
|
spin_unlock_irqrestore(&grp->lock, flags);
|
|
RCU_INIT_POINTER(p->numa_group, NULL);
|
|
put_numa_group(grp);
|
|
}
|
|
|
|
p->numa_faults = NULL;
|
|
kfree(numa_faults);
|
|
}
|
|
|
|
/*
|
|
* Got a PROT_NONE fault for a page on @node.
|
|
*/
|
|
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
|
|
{
|
|
struct task_struct *p = current;
|
|
bool migrated = flags & TNF_MIGRATED;
|
|
int cpu_node = task_node(current);
|
|
int local = !!(flags & TNF_FAULT_LOCAL);
|
|
struct numa_group *ng;
|
|
int priv;
|
|
|
|
if (!static_branch_likely(&sched_numa_balancing))
|
|
return;
|
|
|
|
/* for example, ksmd faulting in a user's mm */
|
|
if (!p->mm)
|
|
return;
|
|
|
|
/* Allocate buffer to track faults on a per-node basis */
|
|
if (unlikely(!p->numa_faults)) {
|
|
int size = sizeof(*p->numa_faults) *
|
|
NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
|
|
|
|
p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
|
|
if (!p->numa_faults)
|
|
return;
|
|
|
|
p->total_numa_faults = 0;
|
|
memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
|
|
}
|
|
|
|
/*
|
|
* First accesses are treated as private, otherwise consider accesses
|
|
* to be private if the accessing pid has not changed
|
|
*/
|
|
if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
|
|
priv = 1;
|
|
} else {
|
|
priv = cpupid_match_pid(p, last_cpupid);
|
|
if (!priv && !(flags & TNF_NO_GROUP))
|
|
task_numa_group(p, last_cpupid, flags, &priv);
|
|
}
|
|
|
|
/*
|
|
* If a workload spans multiple NUMA nodes, a shared fault that
|
|
* occurs wholly within the set of nodes that the workload is
|
|
* actively using should be counted as local. This allows the
|
|
* scan rate to slow down when a workload has settled down.
|
|
*/
|
|
ng = p->numa_group;
|
|
if (!priv && !local && ng && ng->active_nodes > 1 &&
|
|
numa_is_active_node(cpu_node, ng) &&
|
|
numa_is_active_node(mem_node, ng))
|
|
local = 1;
|
|
|
|
/*
|
|
* Retry to migrate task to preferred node periodically, in case it
|
|
* previously failed, or the scheduler moved us.
|
|
*/
|
|
if (time_after(jiffies, p->numa_migrate_retry)) {
|
|
task_numa_placement(p);
|
|
numa_migrate_preferred(p);
|
|
}
|
|
|
|
if (migrated)
|
|
p->numa_pages_migrated += pages;
|
|
if (flags & TNF_MIGRATE_FAIL)
|
|
p->numa_faults_locality[2] += pages;
|
|
|
|
p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
|
|
p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
|
|
p->numa_faults_locality[local] += pages;
|
|
}
|
|
|
|
static void reset_ptenuma_scan(struct task_struct *p)
|
|
{
|
|
/*
|
|
* We only did a read acquisition of the mmap sem, so
|
|
* p->mm->numa_scan_seq is written to without exclusive access
|
|
* and the update is not guaranteed to be atomic. That's not
|
|
* much of an issue though, since this is just used for
|
|
* statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
|
|
* expensive, to avoid any form of compiler optimizations:
|
|
*/
|
|
WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
|
|
p->mm->numa_scan_offset = 0;
|
|
}
|
|
|
|
/*
|
|
* The expensive part of numa migration is done from task_work context.
|
|
* Triggered from task_tick_numa().
|
|
*/
|
|
void task_numa_work(struct callback_head *work)
|
|
{
|
|
unsigned long migrate, next_scan, now = jiffies;
|
|
struct task_struct *p = current;
|
|
struct mm_struct *mm = p->mm;
|
|
u64 runtime = p->se.sum_exec_runtime;
|
|
struct vm_area_struct *vma;
|
|
unsigned long start, end;
|
|
unsigned long nr_pte_updates = 0;
|
|
long pages, virtpages;
|
|
|
|
SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
|
|
|
|
work->next = work; /* protect against double add */
|
|
/*
|
|
* Who cares about NUMA placement when they're dying.
|
|
*
|
|
* NOTE: make sure not to dereference p->mm before this check,
|
|
* exit_task_work() happens _after_ exit_mm() so we could be called
|
|
* without p->mm even though we still had it when we enqueued this
|
|
* work.
|
|
*/
|
|
if (p->flags & PF_EXITING)
|
|
return;
|
|
|
|
if (!mm->numa_next_scan) {
|
|
mm->numa_next_scan = now +
|
|
msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
|
|
}
|
|
|
|
/*
|
|
* Enforce maximal scan/migration frequency..
|
|
*/
|
|
migrate = mm->numa_next_scan;
|
|
if (time_before(now, migrate))
|
|
return;
|
|
|
|
if (p->numa_scan_period == 0) {
|
|
p->numa_scan_period_max = task_scan_max(p);
|
|
p->numa_scan_period = task_scan_start(p);
|
|
}
|
|
|
|
next_scan = now + msecs_to_jiffies(p->numa_scan_period);
|
|
if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
|
|
return;
|
|
|
|
/*
|
|
* Delay this task enough that another task of this mm will likely win
|
|
* the next time around.
|
|
*/
|
|
p->node_stamp += 2 * TICK_NSEC;
|
|
|
|
start = mm->numa_scan_offset;
|
|
pages = sysctl_numa_balancing_scan_size;
|
|
pages <<= 20 - PAGE_SHIFT; /* MB in pages */
|
|
virtpages = pages * 8; /* Scan up to this much virtual space */
|
|
if (!pages)
|
|
return;
|
|
|
|
|
|
if (!down_read_trylock(&mm->mmap_sem))
|
|
return;
|
|
vma = find_vma(mm, start);
|
|
if (!vma) {
|
|
reset_ptenuma_scan(p);
|
|
start = 0;
|
|
vma = mm->mmap;
|
|
}
|
|
for (; vma; vma = vma->vm_next) {
|
|
if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
|
|
is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Shared library pages mapped by multiple processes are not
|
|
* migrated as it is expected they are cache replicated. Avoid
|
|
* hinting faults in read-only file-backed mappings or the vdso
|
|
* as migrating the pages will be of marginal benefit.
|
|
*/
|
|
if (!vma->vm_mm ||
|
|
(vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
|
|
continue;
|
|
|
|
/*
|
|
* Skip inaccessible VMAs to avoid any confusion between
|
|
* PROT_NONE and NUMA hinting ptes
|
|
*/
|
|
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
|
|
continue;
|
|
|
|
do {
|
|
start = max(start, vma->vm_start);
|
|
end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
|
|
end = min(end, vma->vm_end);
|
|
nr_pte_updates = change_prot_numa(vma, start, end);
|
|
|
|
/*
|
|
* Try to scan sysctl_numa_balancing_size worth of
|
|
* hpages that have at least one present PTE that
|
|
* is not already pte-numa. If the VMA contains
|
|
* areas that are unused or already full of prot_numa
|
|
* PTEs, scan up to virtpages, to skip through those
|
|
* areas faster.
|
|
*/
|
|
if (nr_pte_updates)
|
|
pages -= (end - start) >> PAGE_SHIFT;
|
|
virtpages -= (end - start) >> PAGE_SHIFT;
|
|
|
|
start = end;
|
|
if (pages <= 0 || virtpages <= 0)
|
|
goto out;
|
|
|
|
cond_resched();
|
|
} while (end != vma->vm_end);
|
|
}
|
|
|
|
out:
|
|
/*
|
|
* It is possible to reach the end of the VMA list but the last few
|
|
* VMAs are not guaranteed to the vma_migratable. If they are not, we
|
|
* would find the !migratable VMA on the next scan but not reset the
|
|
* scanner to the start so check it now.
|
|
*/
|
|
if (vma)
|
|
mm->numa_scan_offset = start;
|
|
else
|
|
reset_ptenuma_scan(p);
|
|
up_read(&mm->mmap_sem);
|
|
|
|
/*
|
|
* Make sure tasks use at least 32x as much time to run other code
|
|
* than they used here, to limit NUMA PTE scanning overhead to 3% max.
|
|
* Usually update_task_scan_period slows down scanning enough; on an
|
|
* overloaded system we need to limit overhead on a per task basis.
|
|
*/
|
|
if (unlikely(p->se.sum_exec_runtime != runtime)) {
|
|
u64 diff = p->se.sum_exec_runtime - runtime;
|
|
p->node_stamp += 32 * diff;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Drive the periodic memory faults..
|
|
*/
|
|
void task_tick_numa(struct rq *rq, struct task_struct *curr)
|
|
{
|
|
struct callback_head *work = &curr->numa_work;
|
|
u64 period, now;
|
|
|
|
/*
|
|
* We don't care about NUMA placement if we don't have memory.
|
|
*/
|
|
if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
|
|
return;
|
|
|
|
/*
|
|
* Using runtime rather than walltime has the dual advantage that
|
|
* we (mostly) drive the selection from busy threads and that the
|
|
* task needs to have done some actual work before we bother with
|
|
* NUMA placement.
|
|
*/
|
|
now = curr->se.sum_exec_runtime;
|
|
period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
|
|
|
|
if (now > curr->node_stamp + period) {
|
|
if (!curr->node_stamp)
|
|
curr->numa_scan_period = task_scan_start(curr);
|
|
curr->node_stamp += period;
|
|
|
|
if (!time_before(jiffies, curr->mm->numa_next_scan)) {
|
|
init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
|
|
task_work_add(curr, work, true);
|
|
}
|
|
}
|
|
}
|
|
|
|
static void update_scan_period(struct task_struct *p, int new_cpu)
|
|
{
|
|
int src_nid = cpu_to_node(task_cpu(p));
|
|
int dst_nid = cpu_to_node(new_cpu);
|
|
|
|
if (!static_branch_likely(&sched_numa_balancing))
|
|
return;
|
|
|
|
if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
|
|
return;
|
|
|
|
if (src_nid == dst_nid)
|
|
return;
|
|
|
|
/*
|
|
* Allow resets if faults have been trapped before one scan
|
|
* has completed. This is most likely due to a new task that
|
|
* is pulled cross-node due to wakeups or load balancing.
|
|
*/
|
|
if (p->numa_scan_seq) {
|
|
/*
|
|
* Avoid scan adjustments if moving to the preferred
|
|
* node or if the task was not previously running on
|
|
* the preferred node.
|
|
*/
|
|
if (dst_nid == p->numa_preferred_nid ||
|
|
(p->numa_preferred_nid != NUMA_NO_NODE &&
|
|
src_nid != p->numa_preferred_nid))
|
|
return;
|
|
}
|
|
|
|
p->numa_scan_period = task_scan_start(p);
|
|
}
|
|
|
|
#else
|
|
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
|
|
{
|
|
}
|
|
|
|
static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
|
|
{
|
|
}
|
|
|
|
static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
|
|
{
|
|
}
|
|
|
|
static inline void update_scan_period(struct task_struct *p, int new_cpu)
|
|
{
|
|
}
|
|
|
|
#endif /* CONFIG_NUMA_BALANCING */
|
|
|
|
static void
|
|
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
update_load_add(&cfs_rq->load, se->load.weight);
|
|
if (!parent_entity(se))
|
|
update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
|
|
#ifdef CONFIG_SMP
|
|
if (entity_is_task(se)) {
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
|
|
account_numa_enqueue(rq, task_of(se));
|
|
list_add(&se->group_node, &rq->cfs_tasks);
|
|
}
|
|
#endif
|
|
cfs_rq->nr_running++;
|
|
}
|
|
|
|
static void
|
|
account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
update_load_sub(&cfs_rq->load, se->load.weight);
|
|
if (!parent_entity(se))
|
|
update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
|
|
#ifdef CONFIG_SMP
|
|
if (entity_is_task(se)) {
|
|
account_numa_dequeue(rq_of(cfs_rq), task_of(se));
|
|
list_del_init(&se->group_node);
|
|
}
|
|
#endif
|
|
cfs_rq->nr_running--;
|
|
}
|
|
|
|
/*
|
|
* Signed add and clamp on underflow.
|
|
*
|
|
* Explicitly do a load-store to ensure the intermediate value never hits
|
|
* memory. This allows lockless observations without ever seeing the negative
|
|
* values.
|
|
*/
|
|
#define add_positive(_ptr, _val) do { \
|
|
typeof(_ptr) ptr = (_ptr); \
|
|
typeof(_val) val = (_val); \
|
|
typeof(*ptr) res, var = READ_ONCE(*ptr); \
|
|
\
|
|
res = var + val; \
|
|
\
|
|
if (val < 0 && res > var) \
|
|
res = 0; \
|
|
\
|
|
WRITE_ONCE(*ptr, res); \
|
|
} while (0)
|
|
|
|
/*
|
|
* Unsigned subtract and clamp on underflow.
|
|
*
|
|
* Explicitly do a load-store to ensure the intermediate value never hits
|
|
* memory. This allows lockless observations without ever seeing the negative
|
|
* values.
|
|
*/
|
|
#define sub_positive(_ptr, _val) do { \
|
|
typeof(_ptr) ptr = (_ptr); \
|
|
typeof(*ptr) val = (_val); \
|
|
typeof(*ptr) res, var = READ_ONCE(*ptr); \
|
|
res = var - val; \
|
|
if (res > var) \
|
|
res = 0; \
|
|
WRITE_ONCE(*ptr, res); \
|
|
} while (0)
|
|
|
|
/*
|
|
* Remove and clamp on negative, from a local variable.
|
|
*
|
|
* A variant of sub_positive(), which does not use explicit load-store
|
|
* and is thus optimized for local variable updates.
|
|
*/
|
|
#define lsub_positive(_ptr, _val) do { \
|
|
typeof(_ptr) ptr = (_ptr); \
|
|
*ptr -= min_t(typeof(*ptr), *ptr, _val); \
|
|
} while (0)
|
|
|
|
#ifdef CONFIG_SMP
|
|
static inline void
|
|
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
cfs_rq->runnable_weight += se->runnable_weight;
|
|
|
|
cfs_rq->avg.runnable_load_avg += se->avg.runnable_load_avg;
|
|
cfs_rq->avg.runnable_load_sum += se_runnable(se) * se->avg.runnable_load_sum;
|
|
}
|
|
|
|
static inline void
|
|
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
cfs_rq->runnable_weight -= se->runnable_weight;
|
|
|
|
sub_positive(&cfs_rq->avg.runnable_load_avg, se->avg.runnable_load_avg);
|
|
sub_positive(&cfs_rq->avg.runnable_load_sum,
|
|
se_runnable(se) * se->avg.runnable_load_sum);
|
|
}
|
|
|
|
static inline void
|
|
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
cfs_rq->avg.load_avg += se->avg.load_avg;
|
|
cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
|
|
}
|
|
|
|
static inline void
|
|
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
|
|
sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
|
|
}
|
|
#else
|
|
static inline void
|
|
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
|
|
static inline void
|
|
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
|
|
static inline void
|
|
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
|
|
static inline void
|
|
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
|
|
#endif
|
|
|
|
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
|
|
unsigned long weight, unsigned long runnable)
|
|
{
|
|
if (se->on_rq) {
|
|
/* commit outstanding execution time */
|
|
if (cfs_rq->curr == se)
|
|
update_curr(cfs_rq);
|
|
account_entity_dequeue(cfs_rq, se);
|
|
dequeue_runnable_load_avg(cfs_rq, se);
|
|
}
|
|
dequeue_load_avg(cfs_rq, se);
|
|
|
|
se->runnable_weight = runnable;
|
|
update_load_set(&se->load, weight);
|
|
|
|
#ifdef CONFIG_SMP
|
|
do {
|
|
u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib;
|
|
|
|
se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
|
|
se->avg.runnable_load_avg =
|
|
div_u64(se_runnable(se) * se->avg.runnable_load_sum, divider);
|
|
} while (0);
|
|
#endif
|
|
|
|
enqueue_load_avg(cfs_rq, se);
|
|
if (se->on_rq) {
|
|
account_entity_enqueue(cfs_rq, se);
|
|
enqueue_runnable_load_avg(cfs_rq, se);
|
|
}
|
|
}
|
|
|
|
void reweight_task(struct task_struct *p, int prio)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
struct load_weight *load = &se->load;
|
|
unsigned long weight = scale_load(sched_prio_to_weight[prio]);
|
|
|
|
reweight_entity(cfs_rq, se, weight, weight);
|
|
load->inv_weight = sched_prio_to_wmult[prio];
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* All this does is approximate the hierarchical proportion which includes that
|
|
* global sum we all love to hate.
|
|
*
|
|
* That is, the weight of a group entity, is the proportional share of the
|
|
* group weight based on the group runqueue weights. That is:
|
|
*
|
|
* tg->weight * grq->load.weight
|
|
* ge->load.weight = ----------------------------- (1)
|
|
* \Sum grq->load.weight
|
|
*
|
|
* Now, because computing that sum is prohibitively expensive to compute (been
|
|
* there, done that) we approximate it with this average stuff. The average
|
|
* moves slower and therefore the approximation is cheaper and more stable.
|
|
*
|
|
* So instead of the above, we substitute:
|
|
*
|
|
* grq->load.weight -> grq->avg.load_avg (2)
|
|
*
|
|
* which yields the following:
|
|
*
|
|
* tg->weight * grq->avg.load_avg
|
|
* ge->load.weight = ------------------------------ (3)
|
|
* tg->load_avg
|
|
*
|
|
* Where: tg->load_avg ~= \Sum grq->avg.load_avg
|
|
*
|
|
* That is shares_avg, and it is right (given the approximation (2)).
|
|
*
|
|
* The problem with it is that because the average is slow -- it was designed
|
|
* to be exactly that of course -- this leads to transients in boundary
|
|
* conditions. In specific, the case where the group was idle and we start the
|
|
* one task. It takes time for our CPU's grq->avg.load_avg to build up,
|
|
* yielding bad latency etc..
|
|
*
|
|
* Now, in that special case (1) reduces to:
|
|
*
|
|
* tg->weight * grq->load.weight
|
|
* ge->load.weight = ----------------------------- = tg->weight (4)
|
|
* grp->load.weight
|
|
*
|
|
* That is, the sum collapses because all other CPUs are idle; the UP scenario.
|
|
*
|
|
* So what we do is modify our approximation (3) to approach (4) in the (near)
|
|
* UP case, like:
|
|
*
|
|
* ge->load.weight =
|
|
*
|
|
* tg->weight * grq->load.weight
|
|
* --------------------------------------------------- (5)
|
|
* tg->load_avg - grq->avg.load_avg + grq->load.weight
|
|
*
|
|
* But because grq->load.weight can drop to 0, resulting in a divide by zero,
|
|
* we need to use grq->avg.load_avg as its lower bound, which then gives:
|
|
*
|
|
*
|
|
* tg->weight * grq->load.weight
|
|
* ge->load.weight = ----------------------------- (6)
|
|
* tg_load_avg'
|
|
*
|
|
* Where:
|
|
*
|
|
* tg_load_avg' = tg->load_avg - grq->avg.load_avg +
|
|
* max(grq->load.weight, grq->avg.load_avg)
|
|
*
|
|
* And that is shares_weight and is icky. In the (near) UP case it approaches
|
|
* (4) while in the normal case it approaches (3). It consistently
|
|
* overestimates the ge->load.weight and therefore:
|
|
*
|
|
* \Sum ge->load.weight >= tg->weight
|
|
*
|
|
* hence icky!
|
|
*/
|
|
static long calc_group_shares(struct cfs_rq *cfs_rq)
|
|
{
|
|
long tg_weight, tg_shares, load, shares;
|
|
struct task_group *tg = cfs_rq->tg;
|
|
|
|
tg_shares = READ_ONCE(tg->shares);
|
|
|
|
load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
|
|
|
|
tg_weight = atomic_long_read(&tg->load_avg);
|
|
|
|
/* Ensure tg_weight >= load */
|
|
tg_weight -= cfs_rq->tg_load_avg_contrib;
|
|
tg_weight += load;
|
|
|
|
shares = (tg_shares * load);
|
|
if (tg_weight)
|
|
shares /= tg_weight;
|
|
|
|
/*
|
|
* MIN_SHARES has to be unscaled here to support per-CPU partitioning
|
|
* of a group with small tg->shares value. It is a floor value which is
|
|
* assigned as a minimum load.weight to the sched_entity representing
|
|
* the group on a CPU.
|
|
*
|
|
* E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
|
|
* on an 8-core system with 8 tasks each runnable on one CPU shares has
|
|
* to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
|
|
* case no task is runnable on a CPU MIN_SHARES=2 should be returned
|
|
* instead of 0.
|
|
*/
|
|
return clamp_t(long, shares, MIN_SHARES, tg_shares);
|
|
}
|
|
|
|
/*
|
|
* This calculates the effective runnable weight for a group entity based on
|
|
* the group entity weight calculated above.
|
|
*
|
|
* Because of the above approximation (2), our group entity weight is
|
|
* an load_avg based ratio (3). This means that it includes blocked load and
|
|
* does not represent the runnable weight.
|
|
*
|
|
* Approximate the group entity's runnable weight per ratio from the group
|
|
* runqueue:
|
|
*
|
|
* grq->avg.runnable_load_avg
|
|
* ge->runnable_weight = ge->load.weight * -------------------------- (7)
|
|
* grq->avg.load_avg
|
|
*
|
|
* However, analogous to above, since the avg numbers are slow, this leads to
|
|
* transients in the from-idle case. Instead we use:
|
|
*
|
|
* ge->runnable_weight = ge->load.weight *
|
|
*
|
|
* max(grq->avg.runnable_load_avg, grq->runnable_weight)
|
|
* ----------------------------------------------------- (8)
|
|
* max(grq->avg.load_avg, grq->load.weight)
|
|
*
|
|
* Where these max() serve both to use the 'instant' values to fix the slow
|
|
* from-idle and avoid the /0 on to-idle, similar to (6).
|
|
*/
|
|
static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
|
|
{
|
|
long runnable, load_avg;
|
|
|
|
load_avg = max(cfs_rq->avg.load_avg,
|
|
scale_load_down(cfs_rq->load.weight));
|
|
|
|
runnable = max(cfs_rq->avg.runnable_load_avg,
|
|
scale_load_down(cfs_rq->runnable_weight));
|
|
|
|
runnable *= shares;
|
|
if (load_avg)
|
|
runnable /= load_avg;
|
|
|
|
return clamp_t(long, runnable, MIN_SHARES, shares);
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
|
|
|
|
/*
|
|
* Recomputes the group entity based on the current state of its group
|
|
* runqueue.
|
|
*/
|
|
static void update_cfs_group(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *gcfs_rq = group_cfs_rq(se);
|
|
long shares, runnable;
|
|
|
|
if (!gcfs_rq)
|
|
return;
|
|
|
|
if (throttled_hierarchy(gcfs_rq))
|
|
return;
|
|
|
|
#ifndef CONFIG_SMP
|
|
runnable = shares = READ_ONCE(gcfs_rq->tg->shares);
|
|
|
|
if (likely(se->load.weight == shares))
|
|
return;
|
|
#else
|
|
shares = calc_group_shares(gcfs_rq);
|
|
runnable = calc_group_runnable(gcfs_rq, shares);
|
|
#endif
|
|
|
|
reweight_entity(cfs_rq_of(se), se, shares, runnable);
|
|
}
|
|
|
|
#else /* CONFIG_FAIR_GROUP_SCHED */
|
|
static inline void update_cfs_group(struct sched_entity *se)
|
|
{
|
|
}
|
|
#endif /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
|
|
{
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
|
|
if (&rq->cfs == cfs_rq || (flags & SCHED_CPUFREQ_MIGRATION)) {
|
|
/*
|
|
* There are a few boundary cases this might miss but it should
|
|
* get called often enough that that should (hopefully) not be
|
|
* a real problem.
|
|
*
|
|
* It will not get called when we go idle, because the idle
|
|
* thread is a different class (!fair), nor will the utilization
|
|
* number include things like RT tasks.
|
|
*
|
|
* As is, the util number is not freq-invariant (we'd have to
|
|
* implement arch_scale_freq_capacity() for that).
|
|
*
|
|
* See cpu_util().
|
|
*/
|
|
cpufreq_update_util(rq, flags);
|
|
}
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
/**
|
|
* update_tg_load_avg - update the tg's load avg
|
|
* @cfs_rq: the cfs_rq whose avg changed
|
|
* @force: update regardless of how small the difference
|
|
*
|
|
* This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
|
|
* However, because tg->load_avg is a global value there are performance
|
|
* considerations.
|
|
*
|
|
* In order to avoid having to look at the other cfs_rq's, we use a
|
|
* differential update where we store the last value we propagated. This in
|
|
* turn allows skipping updates if the differential is 'small'.
|
|
*
|
|
* Updating tg's load_avg is necessary before update_cfs_share().
|
|
*/
|
|
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
|
|
{
|
|
long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
|
|
|
|
/*
|
|
* No need to update load_avg for root_task_group as it is not used.
|
|
*/
|
|
if (cfs_rq->tg == &root_task_group)
|
|
return;
|
|
|
|
if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
|
|
atomic_long_add(delta, &cfs_rq->tg->load_avg);
|
|
cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Called within set_task_rq() right before setting a task's CPU. The
|
|
* caller only guarantees p->pi_lock is held; no other assumptions,
|
|
* including the state of rq->lock, should be made.
|
|
*/
|
|
void set_task_rq_fair(struct sched_entity *se,
|
|
struct cfs_rq *prev, struct cfs_rq *next)
|
|
{
|
|
u64 p_last_update_time;
|
|
u64 n_last_update_time;
|
|
|
|
if (!sched_feat(ATTACH_AGE_LOAD))
|
|
return;
|
|
|
|
/*
|
|
* We are supposed to update the task to "current" time, then its up to
|
|
* date and ready to go to new CPU/cfs_rq. But we have difficulty in
|
|
* getting what current time is, so simply throw away the out-of-date
|
|
* time. This will result in the wakee task is less decayed, but giving
|
|
* the wakee more load sounds not bad.
|
|
*/
|
|
if (!(se->avg.last_update_time && prev))
|
|
return;
|
|
|
|
#ifndef CONFIG_64BIT
|
|
{
|
|
u64 p_last_update_time_copy;
|
|
u64 n_last_update_time_copy;
|
|
|
|
do {
|
|
p_last_update_time_copy = prev->load_last_update_time_copy;
|
|
n_last_update_time_copy = next->load_last_update_time_copy;
|
|
|
|
smp_rmb();
|
|
|
|
p_last_update_time = prev->avg.last_update_time;
|
|
n_last_update_time = next->avg.last_update_time;
|
|
|
|
} while (p_last_update_time != p_last_update_time_copy ||
|
|
n_last_update_time != n_last_update_time_copy);
|
|
}
|
|
#else
|
|
p_last_update_time = prev->avg.last_update_time;
|
|
n_last_update_time = next->avg.last_update_time;
|
|
#endif
|
|
__update_load_avg_blocked_se(p_last_update_time, se);
|
|
se->avg.last_update_time = n_last_update_time;
|
|
}
|
|
|
|
|
|
/*
|
|
* When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
|
|
* propagate its contribution. The key to this propagation is the invariant
|
|
* that for each group:
|
|
*
|
|
* ge->avg == grq->avg (1)
|
|
*
|
|
* _IFF_ we look at the pure running and runnable sums. Because they
|
|
* represent the very same entity, just at different points in the hierarchy.
|
|
*
|
|
* Per the above update_tg_cfs_util() is trivial and simply copies the running
|
|
* sum over (but still wrong, because the group entity and group rq do not have
|
|
* their PELT windows aligned).
|
|
*
|
|
* However, update_tg_cfs_runnable() is more complex. So we have:
|
|
*
|
|
* ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2)
|
|
*
|
|
* And since, like util, the runnable part should be directly transferable,
|
|
* the following would _appear_ to be the straight forward approach:
|
|
*
|
|
* grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3)
|
|
*
|
|
* And per (1) we have:
|
|
*
|
|
* ge->avg.runnable_avg == grq->avg.runnable_avg
|
|
*
|
|
* Which gives:
|
|
*
|
|
* ge->load.weight * grq->avg.load_avg
|
|
* ge->avg.load_avg = ----------------------------------- (4)
|
|
* grq->load.weight
|
|
*
|
|
* Except that is wrong!
|
|
*
|
|
* Because while for entities historical weight is not important and we
|
|
* really only care about our future and therefore can consider a pure
|
|
* runnable sum, runqueues can NOT do this.
|
|
*
|
|
* We specifically want runqueues to have a load_avg that includes
|
|
* historical weights. Those represent the blocked load, the load we expect
|
|
* to (shortly) return to us. This only works by keeping the weights as
|
|
* integral part of the sum. We therefore cannot decompose as per (3).
|
|
*
|
|
* Another reason this doesn't work is that runnable isn't a 0-sum entity.
|
|
* Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
|
|
* rq itself is runnable anywhere between 2/3 and 1 depending on how the
|
|
* runnable section of these tasks overlap (or not). If they were to perfectly
|
|
* align the rq as a whole would be runnable 2/3 of the time. If however we
|
|
* always have at least 1 runnable task, the rq as a whole is always runnable.
|
|
*
|
|
* So we'll have to approximate.. :/
|
|
*
|
|
* Given the constraint:
|
|
*
|
|
* ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
|
|
*
|
|
* We can construct a rule that adds runnable to a rq by assuming minimal
|
|
* overlap.
|
|
*
|
|
* On removal, we'll assume each task is equally runnable; which yields:
|
|
*
|
|
* grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
|
|
*
|
|
* XXX: only do this for the part of runnable > running ?
|
|
*
|
|
*/
|
|
|
|
static inline void
|
|
update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
|
|
{
|
|
long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
|
|
|
|
/* Nothing to update */
|
|
if (!delta)
|
|
return;
|
|
|
|
/*
|
|
* The relation between sum and avg is:
|
|
*
|
|
* LOAD_AVG_MAX - 1024 + sa->period_contrib
|
|
*
|
|
* however, the PELT windows are not aligned between grq and gse.
|
|
*/
|
|
|
|
/* Set new sched_entity's utilization */
|
|
se->avg.util_avg = gcfs_rq->avg.util_avg;
|
|
se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;
|
|
|
|
/* Update parent cfs_rq utilization */
|
|
add_positive(&cfs_rq->avg.util_avg, delta);
|
|
cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
|
|
}
|
|
|
|
static inline void
|
|
update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
|
|
{
|
|
long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
|
|
unsigned long runnable_load_avg, load_avg;
|
|
u64 runnable_load_sum, load_sum = 0;
|
|
s64 delta_sum;
|
|
|
|
if (!runnable_sum)
|
|
return;
|
|
|
|
gcfs_rq->prop_runnable_sum = 0;
|
|
|
|
if (runnable_sum >= 0) {
|
|
/*
|
|
* Add runnable; clip at LOAD_AVG_MAX. Reflects that until
|
|
* the CPU is saturated running == runnable.
|
|
*/
|
|
runnable_sum += se->avg.load_sum;
|
|
runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
|
|
} else {
|
|
/*
|
|
* Estimate the new unweighted runnable_sum of the gcfs_rq by
|
|
* assuming all tasks are equally runnable.
|
|
*/
|
|
if (scale_load_down(gcfs_rq->load.weight)) {
|
|
load_sum = div_s64(gcfs_rq->avg.load_sum,
|
|
scale_load_down(gcfs_rq->load.weight));
|
|
}
|
|
|
|
/* But make sure to not inflate se's runnable */
|
|
runnable_sum = min(se->avg.load_sum, load_sum);
|
|
}
|
|
|
|
/*
|
|
* runnable_sum can't be lower than running_sum
|
|
* Rescale running sum to be in the same range as runnable sum
|
|
* running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT]
|
|
* runnable_sum is in [0 : LOAD_AVG_MAX]
|
|
*/
|
|
running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
|
|
runnable_sum = max(runnable_sum, running_sum);
|
|
|
|
load_sum = (s64)se_weight(se) * runnable_sum;
|
|
load_avg = div_s64(load_sum, LOAD_AVG_MAX);
|
|
|
|
delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
|
|
delta_avg = load_avg - se->avg.load_avg;
|
|
|
|
se->avg.load_sum = runnable_sum;
|
|
se->avg.load_avg = load_avg;
|
|
add_positive(&cfs_rq->avg.load_avg, delta_avg);
|
|
add_positive(&cfs_rq->avg.load_sum, delta_sum);
|
|
|
|
runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
|
|
runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);
|
|
delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum;
|
|
delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
|
|
|
|
se->avg.runnable_load_sum = runnable_sum;
|
|
se->avg.runnable_load_avg = runnable_load_avg;
|
|
|
|
if (se->on_rq) {
|
|
add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg);
|
|
add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum);
|
|
}
|
|
}
|
|
|
|
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
|
|
{
|
|
cfs_rq->propagate = 1;
|
|
cfs_rq->prop_runnable_sum += runnable_sum;
|
|
}
|
|
|
|
/* Update task and its cfs_rq load average */
|
|
static inline int propagate_entity_load_avg(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *cfs_rq, *gcfs_rq;
|
|
|
|
if (entity_is_task(se))
|
|
return 0;
|
|
|
|
gcfs_rq = group_cfs_rq(se);
|
|
if (!gcfs_rq->propagate)
|
|
return 0;
|
|
|
|
gcfs_rq->propagate = 0;
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
|
|
|
add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
|
|
|
|
update_tg_cfs_util(cfs_rq, se, gcfs_rq);
|
|
update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Check if we need to update the load and the utilization of a blocked
|
|
* group_entity:
|
|
*/
|
|
static inline bool skip_blocked_update(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *gcfs_rq = group_cfs_rq(se);
|
|
|
|
/*
|
|
* If sched_entity still have not zero load or utilization, we have to
|
|
* decay it:
|
|
*/
|
|
if (se->avg.load_avg || se->avg.util_avg)
|
|
return false;
|
|
|
|
/*
|
|
* If there is a pending propagation, we have to update the load and
|
|
* the utilization of the sched_entity:
|
|
*/
|
|
if (gcfs_rq->propagate)
|
|
return false;
|
|
|
|
/*
|
|
* Otherwise, the load and the utilization of the sched_entity is
|
|
* already zero and there is no pending propagation, so it will be a
|
|
* waste of time to try to decay it:
|
|
*/
|
|
return true;
|
|
}
|
|
|
|
#else /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
|
|
|
|
static inline int propagate_entity_load_avg(struct sched_entity *se)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
|
|
|
|
#endif /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
/**
|
|
* update_cfs_rq_load_avg - update the cfs_rq's load/util averages
|
|
* @now: current time, as per cfs_rq_clock_pelt()
|
|
* @cfs_rq: cfs_rq to update
|
|
*
|
|
* The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
|
|
* avg. The immediate corollary is that all (fair) tasks must be attached, see
|
|
* post_init_entity_util_avg().
|
|
*
|
|
* cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
|
|
*
|
|
* Returns true if the load decayed or we removed load.
|
|
*
|
|
* Since both these conditions indicate a changed cfs_rq->avg.load we should
|
|
* call update_tg_load_avg() when this function returns true.
|
|
*/
|
|
static inline int
|
|
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
|
|
{
|
|
unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0;
|
|
struct sched_avg *sa = &cfs_rq->avg;
|
|
int decayed = 0;
|
|
|
|
if (cfs_rq->removed.nr) {
|
|
unsigned long r;
|
|
u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
|
|
|
|
raw_spin_lock(&cfs_rq->removed.lock);
|
|
swap(cfs_rq->removed.util_avg, removed_util);
|
|
swap(cfs_rq->removed.load_avg, removed_load);
|
|
swap(cfs_rq->removed.runnable_sum, removed_runnable_sum);
|
|
cfs_rq->removed.nr = 0;
|
|
raw_spin_unlock(&cfs_rq->removed.lock);
|
|
|
|
r = removed_load;
|
|
sub_positive(&sa->load_avg, r);
|
|
sub_positive(&sa->load_sum, r * divider);
|
|
|
|
r = removed_util;
|
|
sub_positive(&sa->util_avg, r);
|
|
sub_positive(&sa->util_sum, r * divider);
|
|
|
|
add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);
|
|
|
|
decayed = 1;
|
|
}
|
|
|
|
decayed |= __update_load_avg_cfs_rq(now, cfs_rq);
|
|
|
|
#ifndef CONFIG_64BIT
|
|
smp_wmb();
|
|
cfs_rq->load_last_update_time_copy = sa->last_update_time;
|
|
#endif
|
|
|
|
if (decayed)
|
|
cfs_rq_util_change(cfs_rq, 0);
|
|
|
|
return decayed;
|
|
}
|
|
|
|
/**
|
|
* attach_entity_load_avg - attach this entity to its cfs_rq load avg
|
|
* @cfs_rq: cfs_rq to attach to
|
|
* @se: sched_entity to attach
|
|
* @flags: migration hints
|
|
*
|
|
* Must call update_cfs_rq_load_avg() before this, since we rely on
|
|
* cfs_rq->avg.last_update_time being current.
|
|
*/
|
|
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
|
|
{
|
|
u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
|
|
|
|
/*
|
|
* When we attach the @se to the @cfs_rq, we must align the decay
|
|
* window because without that, really weird and wonderful things can
|
|
* happen.
|
|
*
|
|
* XXX illustrate
|
|
*/
|
|
se->avg.last_update_time = cfs_rq->avg.last_update_time;
|
|
se->avg.period_contrib = cfs_rq->avg.period_contrib;
|
|
|
|
/*
|
|
* Hell(o) Nasty stuff.. we need to recompute _sum based on the new
|
|
* period_contrib. This isn't strictly correct, but since we're
|
|
* entirely outside of the PELT hierarchy, nobody cares if we truncate
|
|
* _sum a little.
|
|
*/
|
|
se->avg.util_sum = se->avg.util_avg * divider;
|
|
|
|
se->avg.load_sum = divider;
|
|
if (se_weight(se)) {
|
|
se->avg.load_sum =
|
|
div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
|
|
}
|
|
|
|
se->avg.runnable_load_sum = se->avg.load_sum;
|
|
|
|
enqueue_load_avg(cfs_rq, se);
|
|
cfs_rq->avg.util_avg += se->avg.util_avg;
|
|
cfs_rq->avg.util_sum += se->avg.util_sum;
|
|
|
|
add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
|
|
|
|
cfs_rq_util_change(cfs_rq, flags);
|
|
}
|
|
|
|
/**
|
|
* detach_entity_load_avg - detach this entity from its cfs_rq load avg
|
|
* @cfs_rq: cfs_rq to detach from
|
|
* @se: sched_entity to detach
|
|
*
|
|
* Must call update_cfs_rq_load_avg() before this, since we rely on
|
|
* cfs_rq->avg.last_update_time being current.
|
|
*/
|
|
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
dequeue_load_avg(cfs_rq, se);
|
|
sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
|
|
sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
|
|
|
|
add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
|
|
|
|
cfs_rq_util_change(cfs_rq, 0);
|
|
}
|
|
|
|
/*
|
|
* Optional action to be done while updating the load average
|
|
*/
|
|
#define UPDATE_TG 0x1
|
|
#define SKIP_AGE_LOAD 0x2
|
|
#define DO_ATTACH 0x4
|
|
|
|
/* Update task and its cfs_rq load average */
|
|
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
|
|
{
|
|
u64 now = cfs_rq_clock_pelt(cfs_rq);
|
|
int decayed;
|
|
|
|
/*
|
|
* Track task load average for carrying it to new CPU after migrated, and
|
|
* track group sched_entity load average for task_h_load calc in migration
|
|
*/
|
|
if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
|
|
__update_load_avg_se(now, cfs_rq, se);
|
|
|
|
decayed = update_cfs_rq_load_avg(now, cfs_rq);
|
|
decayed |= propagate_entity_load_avg(se);
|
|
|
|
if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
|
|
|
|
/*
|
|
* DO_ATTACH means we're here from enqueue_entity().
|
|
* !last_update_time means we've passed through
|
|
* migrate_task_rq_fair() indicating we migrated.
|
|
*
|
|
* IOW we're enqueueing a task on a new CPU.
|
|
*/
|
|
attach_entity_load_avg(cfs_rq, se, SCHED_CPUFREQ_MIGRATION);
|
|
update_tg_load_avg(cfs_rq, 0);
|
|
|
|
} else if (decayed && (flags & UPDATE_TG))
|
|
update_tg_load_avg(cfs_rq, 0);
|
|
}
|
|
|
|
#ifndef CONFIG_64BIT
|
|
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
|
|
{
|
|
u64 last_update_time_copy;
|
|
u64 last_update_time;
|
|
|
|
do {
|
|
last_update_time_copy = cfs_rq->load_last_update_time_copy;
|
|
smp_rmb();
|
|
last_update_time = cfs_rq->avg.last_update_time;
|
|
} while (last_update_time != last_update_time_copy);
|
|
|
|
return last_update_time;
|
|
}
|
|
#else
|
|
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
|
|
{
|
|
return cfs_rq->avg.last_update_time;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Synchronize entity load avg of dequeued entity without locking
|
|
* the previous rq.
|
|
*/
|
|
void sync_entity_load_avg(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
u64 last_update_time;
|
|
|
|
last_update_time = cfs_rq_last_update_time(cfs_rq);
|
|
__update_load_avg_blocked_se(last_update_time, se);
|
|
}
|
|
|
|
/*
|
|
* Task first catches up with cfs_rq, and then subtract
|
|
* itself from the cfs_rq (task must be off the queue now).
|
|
*/
|
|
void remove_entity_load_avg(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* tasks cannot exit without having gone through wake_up_new_task() ->
|
|
* post_init_entity_util_avg() which will have added things to the
|
|
* cfs_rq, so we can remove unconditionally.
|
|
*/
|
|
|
|
sync_entity_load_avg(se);
|
|
|
|
raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
|
|
++cfs_rq->removed.nr;
|
|
cfs_rq->removed.util_avg += se->avg.util_avg;
|
|
cfs_rq->removed.load_avg += se->avg.load_avg;
|
|
cfs_rq->removed.runnable_sum += se->avg.load_sum; /* == runnable_sum */
|
|
raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
|
|
}
|
|
|
|
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
|
|
{
|
|
return cfs_rq->avg.runnable_load_avg;
|
|
}
|
|
|
|
static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
|
|
{
|
|
return cfs_rq->avg.load_avg;
|
|
}
|
|
|
|
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
|
|
|
|
static inline unsigned long task_util(struct task_struct *p)
|
|
{
|
|
return READ_ONCE(p->se.avg.util_avg);
|
|
}
|
|
|
|
static inline unsigned long _task_util_est(struct task_struct *p)
|
|
{
|
|
struct util_est ue = READ_ONCE(p->se.avg.util_est);
|
|
|
|
return (max(ue.ewma, ue.enqueued) | UTIL_AVG_UNCHANGED);
|
|
}
|
|
|
|
static inline unsigned long task_util_est(struct task_struct *p)
|
|
{
|
|
return max(task_util(p), _task_util_est(p));
|
|
}
|
|
|
|
static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
|
|
struct task_struct *p)
|
|
{
|
|
unsigned int enqueued;
|
|
|
|
if (!sched_feat(UTIL_EST))
|
|
return;
|
|
|
|
/* Update root cfs_rq's estimated utilization */
|
|
enqueued = cfs_rq->avg.util_est.enqueued;
|
|
enqueued += _task_util_est(p);
|
|
WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
|
|
}
|
|
|
|
/*
|
|
* Check if a (signed) value is within a specified (unsigned) margin,
|
|
* based on the observation that:
|
|
*
|
|
* abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
|
|
*
|
|
* NOTE: this only works when value + maring < INT_MAX.
|
|
*/
|
|
static inline bool within_margin(int value, int margin)
|
|
{
|
|
return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
|
|
}
|
|
|
|
static void
|
|
util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
|
|
{
|
|
long last_ewma_diff;
|
|
struct util_est ue;
|
|
int cpu;
|
|
|
|
if (!sched_feat(UTIL_EST))
|
|
return;
|
|
|
|
/* Update root cfs_rq's estimated utilization */
|
|
ue.enqueued = cfs_rq->avg.util_est.enqueued;
|
|
ue.enqueued -= min_t(unsigned int, ue.enqueued, _task_util_est(p));
|
|
WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);
|
|
|
|
/*
|
|
* Skip update of task's estimated utilization when the task has not
|
|
* yet completed an activation, e.g. being migrated.
|
|
*/
|
|
if (!task_sleep)
|
|
return;
|
|
|
|
/*
|
|
* If the PELT values haven't changed since enqueue time,
|
|
* skip the util_est update.
|
|
*/
|
|
ue = p->se.avg.util_est;
|
|
if (ue.enqueued & UTIL_AVG_UNCHANGED)
|
|
return;
|
|
|
|
/*
|
|
* Skip update of task's estimated utilization when its EWMA is
|
|
* already ~1% close to its last activation value.
|
|
*/
|
|
ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
|
|
last_ewma_diff = ue.enqueued - ue.ewma;
|
|
if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100)))
|
|
return;
|
|
|
|
/*
|
|
* To avoid overestimation of actual task utilization, skip updates if
|
|
* we cannot grant there is idle time in this CPU.
|
|
*/
|
|
cpu = cpu_of(rq_of(cfs_rq));
|
|
if (task_util(p) > capacity_orig_of(cpu))
|
|
return;
|
|
|
|
/*
|
|
* Update Task's estimated utilization
|
|
*
|
|
* When *p completes an activation we can consolidate another sample
|
|
* of the task size. This is done by storing the current PELT value
|
|
* as ue.enqueued and by using this value to update the Exponential
|
|
* Weighted Moving Average (EWMA):
|
|
*
|
|
* ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
|
|
* = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
|
|
* = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
|
|
* = w * ( last_ewma_diff ) + ewma(t-1)
|
|
* = w * (last_ewma_diff + ewma(t-1) / w)
|
|
*
|
|
* Where 'w' is the weight of new samples, which is configured to be
|
|
* 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
|
|
*/
|
|
ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
|
|
ue.ewma += last_ewma_diff;
|
|
ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
|
|
WRITE_ONCE(p->se.avg.util_est, ue);
|
|
}
|
|
|
|
static inline int task_fits_capacity(struct task_struct *p, long capacity)
|
|
{
|
|
return capacity * 1024 > task_util_est(p) * capacity_margin;
|
|
}
|
|
|
|
static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
|
|
{
|
|
if (!static_branch_unlikely(&sched_asym_cpucapacity))
|
|
return;
|
|
|
|
if (!p) {
|
|
rq->misfit_task_load = 0;
|
|
return;
|
|
}
|
|
|
|
if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) {
|
|
rq->misfit_task_load = 0;
|
|
return;
|
|
}
|
|
|
|
rq->misfit_task_load = task_h_load(p);
|
|
}
|
|
|
|
#else /* CONFIG_SMP */
|
|
|
|
#define UPDATE_TG 0x0
|
|
#define SKIP_AGE_LOAD 0x0
|
|
#define DO_ATTACH 0x0
|
|
|
|
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
|
|
{
|
|
cfs_rq_util_change(cfs_rq, 0);
|
|
}
|
|
|
|
static inline void remove_entity_load_avg(struct sched_entity *se) {}
|
|
|
|
static inline void
|
|
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) {}
|
|
static inline void
|
|
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
|
|
|
|
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline void
|
|
util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
|
|
|
|
static inline void
|
|
util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p,
|
|
bool task_sleep) {}
|
|
static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
s64 d = se->vruntime - cfs_rq->min_vruntime;
|
|
|
|
if (d < 0)
|
|
d = -d;
|
|
|
|
if (d > 3*sysctl_sched_latency)
|
|
schedstat_inc(cfs_rq->nr_spread_over);
|
|
#endif
|
|
}
|
|
|
|
static void
|
|
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
|
|
{
|
|
u64 vruntime = cfs_rq->min_vruntime;
|
|
|
|
/*
|
|
* The 'current' period is already promised to the current tasks,
|
|
* however the extra weight of the new task will slow them down a
|
|
* little, place the new task so that it fits in the slot that
|
|
* stays open at the end.
|
|
*/
|
|
if (initial && sched_feat(START_DEBIT))
|
|
vruntime += sched_vslice(cfs_rq, se);
|
|
|
|
/* sleeps up to a single latency don't count. */
|
|
if (!initial) {
|
|
unsigned long thresh = sysctl_sched_latency;
|
|
|
|
/*
|
|
* Halve their sleep time's effect, to allow
|
|
* for a gentler effect of sleepers:
|
|
*/
|
|
if (sched_feat(GENTLE_FAIR_SLEEPERS))
|
|
thresh >>= 1;
|
|
|
|
vruntime -= thresh;
|
|
}
|
|
|
|
/* ensure we never gain time by being placed backwards. */
|
|
se->vruntime = max_vruntime(se->vruntime, vruntime);
|
|
}
|
|
|
|
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
|
|
|
|
static inline void check_schedstat_required(void)
|
|
{
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
if (schedstat_enabled())
|
|
return;
|
|
|
|
/* Force schedstat enabled if a dependent tracepoint is active */
|
|
if (trace_sched_stat_wait_enabled() ||
|
|
trace_sched_stat_sleep_enabled() ||
|
|
trace_sched_stat_iowait_enabled() ||
|
|
trace_sched_stat_blocked_enabled() ||
|
|
trace_sched_stat_runtime_enabled()) {
|
|
printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
|
|
"stat_blocked and stat_runtime require the "
|
|
"kernel parameter schedstats=enable or "
|
|
"kernel.sched_schedstats=1\n");
|
|
}
|
|
#endif
|
|
}
|
|
|
|
|
|
/*
|
|
* MIGRATION
|
|
*
|
|
* dequeue
|
|
* update_curr()
|
|
* update_min_vruntime()
|
|
* vruntime -= min_vruntime
|
|
*
|
|
* enqueue
|
|
* update_curr()
|
|
* update_min_vruntime()
|
|
* vruntime += min_vruntime
|
|
*
|
|
* this way the vruntime transition between RQs is done when both
|
|
* min_vruntime are up-to-date.
|
|
*
|
|
* WAKEUP (remote)
|
|
*
|
|
* ->migrate_task_rq_fair() (p->state == TASK_WAKING)
|
|
* vruntime -= min_vruntime
|
|
*
|
|
* enqueue
|
|
* update_curr()
|
|
* update_min_vruntime()
|
|
* vruntime += min_vruntime
|
|
*
|
|
* this way we don't have the most up-to-date min_vruntime on the originating
|
|
* CPU and an up-to-date min_vruntime on the destination CPU.
|
|
*/
|
|
|
|
static void
|
|
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
|
|
{
|
|
bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
|
|
bool curr = cfs_rq->curr == se;
|
|
|
|
/*
|
|
* If we're the current task, we must renormalise before calling
|
|
* update_curr().
|
|
*/
|
|
if (renorm && curr)
|
|
se->vruntime += cfs_rq->min_vruntime;
|
|
|
|
update_curr(cfs_rq);
|
|
|
|
/*
|
|
* Otherwise, renormalise after, such that we're placed at the current
|
|
* moment in time, instead of some random moment in the past. Being
|
|
* placed in the past could significantly boost this task to the
|
|
* fairness detriment of existing tasks.
|
|
*/
|
|
if (renorm && !curr)
|
|
se->vruntime += cfs_rq->min_vruntime;
|
|
|
|
/*
|
|
* When enqueuing a sched_entity, we must:
|
|
* - Update loads to have both entity and cfs_rq synced with now.
|
|
* - Add its load to cfs_rq->runnable_avg
|
|
* - For group_entity, update its weight to reflect the new share of
|
|
* its group cfs_rq
|
|
* - Add its new weight to cfs_rq->load.weight
|
|
*/
|
|
update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
|
|
update_cfs_group(se);
|
|
enqueue_runnable_load_avg(cfs_rq, se);
|
|
account_entity_enqueue(cfs_rq, se);
|
|
|
|
if (flags & ENQUEUE_WAKEUP)
|
|
place_entity(cfs_rq, se, 0);
|
|
|
|
check_schedstat_required();
|
|
update_stats_enqueue(cfs_rq, se, flags);
|
|
check_spread(cfs_rq, se);
|
|
if (!curr)
|
|
__enqueue_entity(cfs_rq, se);
|
|
se->on_rq = 1;
|
|
|
|
if (cfs_rq->nr_running == 1) {
|
|
list_add_leaf_cfs_rq(cfs_rq);
|
|
check_enqueue_throttle(cfs_rq);
|
|
}
|
|
}
|
|
|
|
static void __clear_buddies_last(struct sched_entity *se)
|
|
{
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
if (cfs_rq->last != se)
|
|
break;
|
|
|
|
cfs_rq->last = NULL;
|
|
}
|
|
}
|
|
|
|
static void __clear_buddies_next(struct sched_entity *se)
|
|
{
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
if (cfs_rq->next != se)
|
|
break;
|
|
|
|
cfs_rq->next = NULL;
|
|
}
|
|
}
|
|
|
|
static void __clear_buddies_skip(struct sched_entity *se)
|
|
{
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
if (cfs_rq->skip != se)
|
|
break;
|
|
|
|
cfs_rq->skip = NULL;
|
|
}
|
|
}
|
|
|
|
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
if (cfs_rq->last == se)
|
|
__clear_buddies_last(se);
|
|
|
|
if (cfs_rq->next == se)
|
|
__clear_buddies_next(se);
|
|
|
|
if (cfs_rq->skip == se)
|
|
__clear_buddies_skip(se);
|
|
}
|
|
|
|
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
|
|
|
|
static void
|
|
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
|
|
{
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
/*
|
|
* When dequeuing a sched_entity, we must:
|
|
* - Update loads to have both entity and cfs_rq synced with now.
|
|
* - Subtract its load from the cfs_rq->runnable_avg.
|
|
* - Subtract its previous weight from cfs_rq->load.weight.
|
|
* - For group entity, update its weight to reflect the new share
|
|
* of its group cfs_rq.
|
|
*/
|
|
update_load_avg(cfs_rq, se, UPDATE_TG);
|
|
dequeue_runnable_load_avg(cfs_rq, se);
|
|
|
|
update_stats_dequeue(cfs_rq, se, flags);
|
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
if (se != cfs_rq->curr)
|
|
__dequeue_entity(cfs_rq, se);
|
|
se->on_rq = 0;
|
|
account_entity_dequeue(cfs_rq, se);
|
|
|
|
/*
|
|
* Normalize after update_curr(); which will also have moved
|
|
* min_vruntime if @se is the one holding it back. But before doing
|
|
* update_min_vruntime() again, which will discount @se's position and
|
|
* can move min_vruntime forward still more.
|
|
*/
|
|
if (!(flags & DEQUEUE_SLEEP))
|
|
se->vruntime -= cfs_rq->min_vruntime;
|
|
|
|
/* return excess runtime on last dequeue */
|
|
return_cfs_rq_runtime(cfs_rq);
|
|
|
|
update_cfs_group(se);
|
|
|
|
/*
|
|
* Now advance min_vruntime if @se was the entity holding it back,
|
|
* except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
|
|
* put back on, and if we advance min_vruntime, we'll be placed back
|
|
* further than we started -- ie. we'll be penalized.
|
|
*/
|
|
if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
|
|
update_min_vruntime(cfs_rq);
|
|
}
|
|
|
|
/*
|
|
* Preempt the current task with a newly woken task if needed:
|
|
*/
|
|
static void
|
|
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
|
|
{
|
|
unsigned long ideal_runtime, delta_exec;
|
|
struct sched_entity *se;
|
|
s64 delta;
|
|
|
|
ideal_runtime = sched_slice(cfs_rq, curr);
|
|
delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
|
|
if (delta_exec > ideal_runtime) {
|
|
resched_curr(rq_of(cfs_rq));
|
|
/*
|
|
* The current task ran long enough, ensure it doesn't get
|
|
* re-elected due to buddy favours.
|
|
*/
|
|
clear_buddies(cfs_rq, curr);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Ensure that a task that missed wakeup preemption by a
|
|
* narrow margin doesn't have to wait for a full slice.
|
|
* This also mitigates buddy induced latencies under load.
|
|
*/
|
|
if (delta_exec < sysctl_sched_min_granularity)
|
|
return;
|
|
|
|
se = __pick_first_entity(cfs_rq);
|
|
delta = curr->vruntime - se->vruntime;
|
|
|
|
if (delta < 0)
|
|
return;
|
|
|
|
if (delta > ideal_runtime)
|
|
resched_curr(rq_of(cfs_rq));
|
|
}
|
|
|
|
static void
|
|
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/* 'current' is not kept within the tree. */
|
|
if (se->on_rq) {
|
|
/*
|
|
* Any task has to be enqueued before it get to execute on
|
|
* a CPU. So account for the time it spent waiting on the
|
|
* runqueue.
|
|
*/
|
|
update_stats_wait_end(cfs_rq, se);
|
|
__dequeue_entity(cfs_rq, se);
|
|
update_load_avg(cfs_rq, se, UPDATE_TG);
|
|
}
|
|
|
|
update_stats_curr_start(cfs_rq, se);
|
|
cfs_rq->curr = se;
|
|
|
|
/*
|
|
* Track our maximum slice length, if the CPU's load is at
|
|
* least twice that of our own weight (i.e. dont track it
|
|
* when there are only lesser-weight tasks around):
|
|
*/
|
|
if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
|
|
schedstat_set(se->statistics.slice_max,
|
|
max((u64)schedstat_val(se->statistics.slice_max),
|
|
se->sum_exec_runtime - se->prev_sum_exec_runtime));
|
|
}
|
|
|
|
se->prev_sum_exec_runtime = se->sum_exec_runtime;
|
|
}
|
|
|
|
static int
|
|
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
|
|
|
|
/*
|
|
* Pick the next process, keeping these things in mind, in this order:
|
|
* 1) keep things fair between processes/task groups
|
|
* 2) pick the "next" process, since someone really wants that to run
|
|
* 3) pick the "last" process, for cache locality
|
|
* 4) do not run the "skip" process, if something else is available
|
|
*/
|
|
static struct sched_entity *
|
|
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
|
|
{
|
|
struct sched_entity *left = __pick_first_entity(cfs_rq);
|
|
struct sched_entity *se;
|
|
|
|
/*
|
|
* If curr is set we have to see if its left of the leftmost entity
|
|
* still in the tree, provided there was anything in the tree at all.
|
|
*/
|
|
if (!left || (curr && entity_before(curr, left)))
|
|
left = curr;
|
|
|
|
se = left; /* ideally we run the leftmost entity */
|
|
|
|
/*
|
|
* Avoid running the skip buddy, if running something else can
|
|
* be done without getting too unfair.
|
|
*/
|
|
if (cfs_rq->skip == se) {
|
|
struct sched_entity *second;
|
|
|
|
if (se == curr) {
|
|
second = __pick_first_entity(cfs_rq);
|
|
} else {
|
|
second = __pick_next_entity(se);
|
|
if (!second || (curr && entity_before(curr, second)))
|
|
second = curr;
|
|
}
|
|
|
|
if (second && wakeup_preempt_entity(second, left) < 1)
|
|
se = second;
|
|
}
|
|
|
|
/*
|
|
* Prefer last buddy, try to return the CPU to a preempted task.
|
|
*/
|
|
if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
|
|
se = cfs_rq->last;
|
|
|
|
/*
|
|
* Someone really wants this to run. If it's not unfair, run it.
|
|
*/
|
|
if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
|
|
se = cfs_rq->next;
|
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
return se;
|
|
}
|
|
|
|
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
|
|
|
|
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
|
|
{
|
|
/*
|
|
* If still on the runqueue then deactivate_task()
|
|
* was not called and update_curr() has to be done:
|
|
*/
|
|
if (prev->on_rq)
|
|
update_curr(cfs_rq);
|
|
|
|
/* throttle cfs_rqs exceeding runtime */
|
|
check_cfs_rq_runtime(cfs_rq);
|
|
|
|
check_spread(cfs_rq, prev);
|
|
|
|
if (prev->on_rq) {
|
|
update_stats_wait_start(cfs_rq, prev);
|
|
/* Put 'current' back into the tree. */
|
|
__enqueue_entity(cfs_rq, prev);
|
|
/* in !on_rq case, update occurred at dequeue */
|
|
update_load_avg(cfs_rq, prev, 0);
|
|
}
|
|
cfs_rq->curr = NULL;
|
|
}
|
|
|
|
static void
|
|
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
|
|
{
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
/*
|
|
* Ensure that runnable average is periodically updated.
|
|
*/
|
|
update_load_avg(cfs_rq, curr, UPDATE_TG);
|
|
update_cfs_group(curr);
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
/*
|
|
* queued ticks are scheduled to match the slice, so don't bother
|
|
* validating it and just reschedule.
|
|
*/
|
|
if (queued) {
|
|
resched_curr(rq_of(cfs_rq));
|
|
return;
|
|
}
|
|
/*
|
|
* don't let the period tick interfere with the hrtick preemption
|
|
*/
|
|
if (!sched_feat(DOUBLE_TICK) &&
|
|
hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
|
|
return;
|
|
#endif
|
|
|
|
if (cfs_rq->nr_running > 1)
|
|
check_preempt_tick(cfs_rq, curr);
|
|
}
|
|
|
|
|
|
/**************************************************
|
|
* CFS bandwidth control machinery
|
|
*/
|
|
|
|
#ifdef CONFIG_CFS_BANDWIDTH
|
|
|
|
#ifdef CONFIG_JUMP_LABEL
|
|
static struct static_key __cfs_bandwidth_used;
|
|
|
|
static inline bool cfs_bandwidth_used(void)
|
|
{
|
|
return static_key_false(&__cfs_bandwidth_used);
|
|
}
|
|
|
|
void cfs_bandwidth_usage_inc(void)
|
|
{
|
|
static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
|
|
}
|
|
|
|
void cfs_bandwidth_usage_dec(void)
|
|
{
|
|
static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
|
|
}
|
|
#else /* CONFIG_JUMP_LABEL */
|
|
static bool cfs_bandwidth_used(void)
|
|
{
|
|
return true;
|
|
}
|
|
|
|
void cfs_bandwidth_usage_inc(void) {}
|
|
void cfs_bandwidth_usage_dec(void) {}
|
|
#endif /* CONFIG_JUMP_LABEL */
|
|
|
|
/*
|
|
* default period for cfs group bandwidth.
|
|
* default: 0.1s, units: nanoseconds
|
|
*/
|
|
static inline u64 default_cfs_period(void)
|
|
{
|
|
return 100000000ULL;
|
|
}
|
|
|
|
static inline u64 sched_cfs_bandwidth_slice(void)
|
|
{
|
|
return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
|
|
}
|
|
|
|
/*
|
|
* Replenish runtime according to assigned quota and update expiration time.
|
|
* We use sched_clock_cpu directly instead of rq->clock to avoid adding
|
|
* additional synchronization around rq->lock.
|
|
*
|
|
* requires cfs_b->lock
|
|
*/
|
|
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
u64 now;
|
|
|
|
if (cfs_b->quota == RUNTIME_INF)
|
|
return;
|
|
|
|
now = sched_clock_cpu(smp_processor_id());
|
|
cfs_b->runtime = cfs_b->quota;
|
|
cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
|
|
cfs_b->expires_seq++;
|
|
}
|
|
|
|
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
|
|
{
|
|
return &tg->cfs_bandwidth;
|
|
}
|
|
|
|
/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
|
|
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (unlikely(cfs_rq->throttle_count))
|
|
return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
|
|
|
|
return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
|
|
}
|
|
|
|
/* returns 0 on failure to allocate runtime */
|
|
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct task_group *tg = cfs_rq->tg;
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
|
|
u64 amount = 0, min_amount, expires;
|
|
int expires_seq;
|
|
|
|
/* note: this is a positive sum as runtime_remaining <= 0 */
|
|
min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
|
|
|
|
raw_spin_lock(&cfs_b->lock);
|
|
if (cfs_b->quota == RUNTIME_INF)
|
|
amount = min_amount;
|
|
else {
|
|
start_cfs_bandwidth(cfs_b);
|
|
|
|
if (cfs_b->runtime > 0) {
|
|
amount = min(cfs_b->runtime, min_amount);
|
|
cfs_b->runtime -= amount;
|
|
cfs_b->idle = 0;
|
|
}
|
|
}
|
|
expires_seq = cfs_b->expires_seq;
|
|
expires = cfs_b->runtime_expires;
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
|
|
cfs_rq->runtime_remaining += amount;
|
|
/*
|
|
* we may have advanced our local expiration to account for allowed
|
|
* spread between our sched_clock and the one on which runtime was
|
|
* issued.
|
|
*/
|
|
if (cfs_rq->expires_seq != expires_seq) {
|
|
cfs_rq->expires_seq = expires_seq;
|
|
cfs_rq->runtime_expires = expires;
|
|
}
|
|
|
|
return cfs_rq->runtime_remaining > 0;
|
|
}
|
|
|
|
/*
|
|
* Note: This depends on the synchronization provided by sched_clock and the
|
|
* fact that rq->clock snapshots this value.
|
|
*/
|
|
static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
|
|
|
|
/* if the deadline is ahead of our clock, nothing to do */
|
|
if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
|
|
return;
|
|
|
|
if (cfs_rq->runtime_remaining < 0)
|
|
return;
|
|
|
|
/*
|
|
* If the local deadline has passed we have to consider the
|
|
* possibility that our sched_clock is 'fast' and the global deadline
|
|
* has not truly expired.
|
|
*
|
|
* Fortunately we can check determine whether this the case by checking
|
|
* whether the global deadline(cfs_b->expires_seq) has advanced.
|
|
*/
|
|
if (cfs_rq->expires_seq == cfs_b->expires_seq) {
|
|
/* extend local deadline, drift is bounded above by 2 ticks */
|
|
cfs_rq->runtime_expires += TICK_NSEC;
|
|
} else {
|
|
/* global deadline is ahead, expiration has passed */
|
|
cfs_rq->runtime_remaining = 0;
|
|
}
|
|
}
|
|
|
|
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
|
|
{
|
|
/* dock delta_exec before expiring quota (as it could span periods) */
|
|
cfs_rq->runtime_remaining -= delta_exec;
|
|
expire_cfs_rq_runtime(cfs_rq);
|
|
|
|
if (likely(cfs_rq->runtime_remaining > 0))
|
|
return;
|
|
|
|
/*
|
|
* if we're unable to extend our runtime we resched so that the active
|
|
* hierarchy can be throttled
|
|
*/
|
|
if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
|
|
resched_curr(rq_of(cfs_rq));
|
|
}
|
|
|
|
static __always_inline
|
|
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
|
|
{
|
|
if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
|
|
return;
|
|
|
|
__account_cfs_rq_runtime(cfs_rq, delta_exec);
|
|
}
|
|
|
|
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
|
|
{
|
|
return cfs_bandwidth_used() && cfs_rq->throttled;
|
|
}
|
|
|
|
/* check whether cfs_rq, or any parent, is throttled */
|
|
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
|
|
{
|
|
return cfs_bandwidth_used() && cfs_rq->throttle_count;
|
|
}
|
|
|
|
/*
|
|
* Ensure that neither of the group entities corresponding to src_cpu or
|
|
* dest_cpu are members of a throttled hierarchy when performing group
|
|
* load-balance operations.
|
|
*/
|
|
static inline int throttled_lb_pair(struct task_group *tg,
|
|
int src_cpu, int dest_cpu)
|
|
{
|
|
struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
|
|
|
|
src_cfs_rq = tg->cfs_rq[src_cpu];
|
|
dest_cfs_rq = tg->cfs_rq[dest_cpu];
|
|
|
|
return throttled_hierarchy(src_cfs_rq) ||
|
|
throttled_hierarchy(dest_cfs_rq);
|
|
}
|
|
|
|
static int tg_unthrottle_up(struct task_group *tg, void *data)
|
|
{
|
|
struct rq *rq = data;
|
|
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
|
|
|
|
cfs_rq->throttle_count--;
|
|
if (!cfs_rq->throttle_count) {
|
|
/* adjust cfs_rq_clock_task() */
|
|
cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
|
|
cfs_rq->throttled_clock_task;
|
|
|
|
/* Add cfs_rq with already running entity in the list */
|
|
if (cfs_rq->nr_running >= 1)
|
|
list_add_leaf_cfs_rq(cfs_rq);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int tg_throttle_down(struct task_group *tg, void *data)
|
|
{
|
|
struct rq *rq = data;
|
|
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
|
|
|
|
/* group is entering throttled state, stop time */
|
|
if (!cfs_rq->throttle_count) {
|
|
cfs_rq->throttled_clock_task = rq_clock_task(rq);
|
|
list_del_leaf_cfs_rq(cfs_rq);
|
|
}
|
|
cfs_rq->throttle_count++;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
|
|
struct sched_entity *se;
|
|
long task_delta, dequeue = 1;
|
|
bool empty;
|
|
|
|
se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
|
|
|
|
/* freeze hierarchy runnable averages while throttled */
|
|
rcu_read_lock();
|
|
walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
|
|
rcu_read_unlock();
|
|
|
|
task_delta = cfs_rq->h_nr_running;
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *qcfs_rq = cfs_rq_of(se);
|
|
/* throttled entity or throttle-on-deactivate */
|
|
if (!se->on_rq)
|
|
break;
|
|
|
|
if (dequeue)
|
|
dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
|
|
qcfs_rq->h_nr_running -= task_delta;
|
|
|
|
if (qcfs_rq->load.weight)
|
|
dequeue = 0;
|
|
}
|
|
|
|
if (!se)
|
|
sub_nr_running(rq, task_delta);
|
|
|
|
cfs_rq->throttled = 1;
|
|
cfs_rq->throttled_clock = rq_clock(rq);
|
|
raw_spin_lock(&cfs_b->lock);
|
|
empty = list_empty(&cfs_b->throttled_cfs_rq);
|
|
|
|
/*
|
|
* Add to the _head_ of the list, so that an already-started
|
|
* distribute_cfs_runtime will not see us. If disribute_cfs_runtime is
|
|
* not running add to the tail so that later runqueues don't get starved.
|
|
*/
|
|
if (cfs_b->distribute_running)
|
|
list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
|
|
else
|
|
list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
|
|
|
|
/*
|
|
* If we're the first throttled task, make sure the bandwidth
|
|
* timer is running.
|
|
*/
|
|
if (empty)
|
|
start_cfs_bandwidth(cfs_b);
|
|
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
}
|
|
|
|
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
|
|
struct sched_entity *se;
|
|
int enqueue = 1;
|
|
long task_delta;
|
|
|
|
se = cfs_rq->tg->se[cpu_of(rq)];
|
|
|
|
cfs_rq->throttled = 0;
|
|
|
|
update_rq_clock(rq);
|
|
|
|
raw_spin_lock(&cfs_b->lock);
|
|
cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
|
|
list_del_rcu(&cfs_rq->throttled_list);
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
|
|
/* update hierarchical throttle state */
|
|
walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
|
|
|
|
if (!cfs_rq->load.weight)
|
|
return;
|
|
|
|
task_delta = cfs_rq->h_nr_running;
|
|
for_each_sched_entity(se) {
|
|
if (se->on_rq)
|
|
enqueue = 0;
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
|
if (enqueue)
|
|
enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
|
|
cfs_rq->h_nr_running += task_delta;
|
|
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
}
|
|
|
|
assert_list_leaf_cfs_rq(rq);
|
|
|
|
if (!se)
|
|
add_nr_running(rq, task_delta);
|
|
|
|
/* Determine whether we need to wake up potentially idle CPU: */
|
|
if (rq->curr == rq->idle && rq->cfs.nr_running)
|
|
resched_curr(rq);
|
|
}
|
|
|
|
static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
|
|
u64 remaining, u64 expires)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
u64 runtime;
|
|
u64 starting_runtime = remaining;
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
|
|
throttled_list) {
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
struct rq_flags rf;
|
|
|
|
rq_lock_irqsave(rq, &rf);
|
|
if (!cfs_rq_throttled(cfs_rq))
|
|
goto next;
|
|
|
|
runtime = -cfs_rq->runtime_remaining + 1;
|
|
if (runtime > remaining)
|
|
runtime = remaining;
|
|
remaining -= runtime;
|
|
|
|
cfs_rq->runtime_remaining += runtime;
|
|
cfs_rq->runtime_expires = expires;
|
|
|
|
/* we check whether we're throttled above */
|
|
if (cfs_rq->runtime_remaining > 0)
|
|
unthrottle_cfs_rq(cfs_rq);
|
|
|
|
next:
|
|
rq_unlock_irqrestore(rq, &rf);
|
|
|
|
if (!remaining)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return starting_runtime - remaining;
|
|
}
|
|
|
|
/*
|
|
* Responsible for refilling a task_group's bandwidth and unthrottling its
|
|
* cfs_rqs as appropriate. If there has been no activity within the last
|
|
* period the timer is deactivated until scheduling resumes; cfs_b->idle is
|
|
* used to track this state.
|
|
*/
|
|
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
|
|
{
|
|
u64 runtime, runtime_expires;
|
|
int throttled;
|
|
|
|
/* no need to continue the timer with no bandwidth constraint */
|
|
if (cfs_b->quota == RUNTIME_INF)
|
|
goto out_deactivate;
|
|
|
|
throttled = !list_empty(&cfs_b->throttled_cfs_rq);
|
|
cfs_b->nr_periods += overrun;
|
|
|
|
/*
|
|
* idle depends on !throttled (for the case of a large deficit), and if
|
|
* we're going inactive then everything else can be deferred
|
|
*/
|
|
if (cfs_b->idle && !throttled)
|
|
goto out_deactivate;
|
|
|
|
__refill_cfs_bandwidth_runtime(cfs_b);
|
|
|
|
if (!throttled) {
|
|
/* mark as potentially idle for the upcoming period */
|
|
cfs_b->idle = 1;
|
|
return 0;
|
|
}
|
|
|
|
/* account preceding periods in which throttling occurred */
|
|
cfs_b->nr_throttled += overrun;
|
|
|
|
runtime_expires = cfs_b->runtime_expires;
|
|
|
|
/*
|
|
* This check is repeated as we are holding onto the new bandwidth while
|
|
* we unthrottle. This can potentially race with an unthrottled group
|
|
* trying to acquire new bandwidth from the global pool. This can result
|
|
* in us over-using our runtime if it is all used during this loop, but
|
|
* only by limited amounts in that extreme case.
|
|
*/
|
|
while (throttled && cfs_b->runtime > 0 && !cfs_b->distribute_running) {
|
|
runtime = cfs_b->runtime;
|
|
cfs_b->distribute_running = 1;
|
|
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
|
|
/* we can't nest cfs_b->lock while distributing bandwidth */
|
|
runtime = distribute_cfs_runtime(cfs_b, runtime,
|
|
runtime_expires);
|
|
raw_spin_lock_irqsave(&cfs_b->lock, flags);
|
|
|
|
cfs_b->distribute_running = 0;
|
|
throttled = !list_empty(&cfs_b->throttled_cfs_rq);
|
|
|
|
lsub_positive(&cfs_b->runtime, runtime);
|
|
}
|
|
|
|
/*
|
|
* While we are ensured activity in the period following an
|
|
* unthrottle, this also covers the case in which the new bandwidth is
|
|
* insufficient to cover the existing bandwidth deficit. (Forcing the
|
|
* timer to remain active while there are any throttled entities.)
|
|
*/
|
|
cfs_b->idle = 0;
|
|
|
|
return 0;
|
|
|
|
out_deactivate:
|
|
return 1;
|
|
}
|
|
|
|
/* a cfs_rq won't donate quota below this amount */
|
|
static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
|
|
/* minimum remaining period time to redistribute slack quota */
|
|
static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
|
|
/* how long we wait to gather additional slack before distributing */
|
|
static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
|
|
|
|
/*
|
|
* Are we near the end of the current quota period?
|
|
*
|
|
* Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
|
|
* hrtimer base being cleared by hrtimer_start. In the case of
|
|
* migrate_hrtimers, base is never cleared, so we are fine.
|
|
*/
|
|
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
|
|
{
|
|
struct hrtimer *refresh_timer = &cfs_b->period_timer;
|
|
u64 remaining;
|
|
|
|
/* if the call-back is running a quota refresh is already occurring */
|
|
if (hrtimer_callback_running(refresh_timer))
|
|
return 1;
|
|
|
|
/* is a quota refresh about to occur? */
|
|
remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
|
|
if (remaining < min_expire)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
|
|
|
|
/* if there's a quota refresh soon don't bother with slack */
|
|
if (runtime_refresh_within(cfs_b, min_left))
|
|
return;
|
|
|
|
hrtimer_start(&cfs_b->slack_timer,
|
|
ns_to_ktime(cfs_bandwidth_slack_period),
|
|
HRTIMER_MODE_REL);
|
|
}
|
|
|
|
/* we know any runtime found here is valid as update_curr() precedes return */
|
|
static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
|
|
s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
|
|
|
|
if (slack_runtime <= 0)
|
|
return;
|
|
|
|
raw_spin_lock(&cfs_b->lock);
|
|
if (cfs_b->quota != RUNTIME_INF &&
|
|
cfs_rq->runtime_expires == cfs_b->runtime_expires) {
|
|
cfs_b->runtime += slack_runtime;
|
|
|
|
/* we are under rq->lock, defer unthrottling using a timer */
|
|
if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
|
|
!list_empty(&cfs_b->throttled_cfs_rq))
|
|
start_cfs_slack_bandwidth(cfs_b);
|
|
}
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
|
|
/* even if it's not valid for return we don't want to try again */
|
|
cfs_rq->runtime_remaining -= slack_runtime;
|
|
}
|
|
|
|
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (!cfs_bandwidth_used())
|
|
return;
|
|
|
|
if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
|
|
return;
|
|
|
|
__return_cfs_rq_runtime(cfs_rq);
|
|
}
|
|
|
|
/*
|
|
* This is done with a timer (instead of inline with bandwidth return) since
|
|
* it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
|
|
*/
|
|
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
|
|
unsigned long flags;
|
|
u64 expires;
|
|
|
|
/* confirm we're still not at a refresh boundary */
|
|
raw_spin_lock_irqsave(&cfs_b->lock, flags);
|
|
if (cfs_b->distribute_running) {
|
|
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
|
|
return;
|
|
}
|
|
|
|
if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
|
|
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
|
|
return;
|
|
}
|
|
|
|
if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
|
|
runtime = cfs_b->runtime;
|
|
|
|
expires = cfs_b->runtime_expires;
|
|
if (runtime)
|
|
cfs_b->distribute_running = 1;
|
|
|
|
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
|
|
|
|
if (!runtime)
|
|
return;
|
|
|
|
runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
|
|
|
|
raw_spin_lock_irqsave(&cfs_b->lock, flags);
|
|
if (expires == cfs_b->runtime_expires)
|
|
lsub_positive(&cfs_b->runtime, runtime);
|
|
cfs_b->distribute_running = 0;
|
|
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* When a group wakes up we want to make sure that its quota is not already
|
|
* expired/exceeded, otherwise it may be allowed to steal additional ticks of
|
|
* runtime as update_curr() throttling can not not trigger until it's on-rq.
|
|
*/
|
|
static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (!cfs_bandwidth_used())
|
|
return;
|
|
|
|
/* an active group must be handled by the update_curr()->put() path */
|
|
if (!cfs_rq->runtime_enabled || cfs_rq->curr)
|
|
return;
|
|
|
|
/* ensure the group is not already throttled */
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
return;
|
|
|
|
/* update runtime allocation */
|
|
account_cfs_rq_runtime(cfs_rq, 0);
|
|
if (cfs_rq->runtime_remaining <= 0)
|
|
throttle_cfs_rq(cfs_rq);
|
|
}
|
|
|
|
static void sync_throttle(struct task_group *tg, int cpu)
|
|
{
|
|
struct cfs_rq *pcfs_rq, *cfs_rq;
|
|
|
|
if (!cfs_bandwidth_used())
|
|
return;
|
|
|
|
if (!tg->parent)
|
|
return;
|
|
|
|
cfs_rq = tg->cfs_rq[cpu];
|
|
pcfs_rq = tg->parent->cfs_rq[cpu];
|
|
|
|
cfs_rq->throttle_count = pcfs_rq->throttle_count;
|
|
cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
|
|
}
|
|
|
|
/* conditionally throttle active cfs_rq's from put_prev_entity() */
|
|
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (!cfs_bandwidth_used())
|
|
return false;
|
|
|
|
if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
|
|
return false;
|
|
|
|
/*
|
|
* it's possible for a throttled entity to be forced into a running
|
|
* state (e.g. set_curr_task), in this case we're finished.
|
|
*/
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
return true;
|
|
|
|
throttle_cfs_rq(cfs_rq);
|
|
return true;
|
|
}
|
|
|
|
static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
|
|
{
|
|
struct cfs_bandwidth *cfs_b =
|
|
container_of(timer, struct cfs_bandwidth, slack_timer);
|
|
|
|
do_sched_cfs_slack_timer(cfs_b);
|
|
|
|
return HRTIMER_NORESTART;
|
|
}
|
|
|
|
static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
|
|
{
|
|
struct cfs_bandwidth *cfs_b =
|
|
container_of(timer, struct cfs_bandwidth, period_timer);
|
|
unsigned long flags;
|
|
int overrun;
|
|
int idle = 0;
|
|
|
|
raw_spin_lock_irqsave(&cfs_b->lock, flags);
|
|
for (;;) {
|
|
overrun = hrtimer_forward_now(timer, cfs_b->period);
|
|
if (!overrun)
|
|
break;
|
|
|
|
idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
|
|
}
|
|
if (idle)
|
|
cfs_b->period_active = 0;
|
|
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
|
|
|
|
return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
|
|
}
|
|
|
|
void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
raw_spin_lock_init(&cfs_b->lock);
|
|
cfs_b->runtime = 0;
|
|
cfs_b->quota = RUNTIME_INF;
|
|
cfs_b->period = ns_to_ktime(default_cfs_period());
|
|
|
|
INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
|
|
hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
|
|
cfs_b->period_timer.function = sched_cfs_period_timer;
|
|
hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
|
|
cfs_b->slack_timer.function = sched_cfs_slack_timer;
|
|
cfs_b->distribute_running = 0;
|
|
}
|
|
|
|
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
|
|
{
|
|
cfs_rq->runtime_enabled = 0;
|
|
INIT_LIST_HEAD(&cfs_rq->throttled_list);
|
|
}
|
|
|
|
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
u64 overrun;
|
|
|
|
lockdep_assert_held(&cfs_b->lock);
|
|
|
|
if (cfs_b->period_active)
|
|
return;
|
|
|
|
cfs_b->period_active = 1;
|
|
overrun = hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
|
|
cfs_b->runtime_expires += (overrun + 1) * ktime_to_ns(cfs_b->period);
|
|
cfs_b->expires_seq++;
|
|
hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
|
|
}
|
|
|
|
static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
|
|
{
|
|
/* init_cfs_bandwidth() was not called */
|
|
if (!cfs_b->throttled_cfs_rq.next)
|
|
return;
|
|
|
|
hrtimer_cancel(&cfs_b->period_timer);
|
|
hrtimer_cancel(&cfs_b->slack_timer);
|
|
}
|
|
|
|
/*
|
|
* Both these CPU hotplug callbacks race against unregister_fair_sched_group()
|
|
*
|
|
* The race is harmless, since modifying bandwidth settings of unhooked group
|
|
* bits doesn't do much.
|
|
*/
|
|
|
|
/* cpu online calback */
|
|
static void __maybe_unused update_runtime_enabled(struct rq *rq)
|
|
{
|
|
struct task_group *tg;
|
|
|
|
lockdep_assert_held(&rq->lock);
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(tg, &task_groups, list) {
|
|
struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
|
|
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
|
|
|
|
raw_spin_lock(&cfs_b->lock);
|
|
cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
|
|
raw_spin_unlock(&cfs_b->lock);
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/* cpu offline callback */
|
|
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
|
|
{
|
|
struct task_group *tg;
|
|
|
|
lockdep_assert_held(&rq->lock);
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(tg, &task_groups, list) {
|
|
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
|
|
|
|
if (!cfs_rq->runtime_enabled)
|
|
continue;
|
|
|
|
/*
|
|
* clock_task is not advancing so we just need to make sure
|
|
* there's some valid quota amount
|
|
*/
|
|
cfs_rq->runtime_remaining = 1;
|
|
/*
|
|
* Offline rq is schedulable till CPU is completely disabled
|
|
* in take_cpu_down(), so we prevent new cfs throttling here.
|
|
*/
|
|
cfs_rq->runtime_enabled = 0;
|
|
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
unthrottle_cfs_rq(cfs_rq);
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
#else /* CONFIG_CFS_BANDWIDTH */
|
|
|
|
static inline bool cfs_bandwidth_used(void)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
|
|
{
|
|
return rq_clock_task(rq_of(cfs_rq));
|
|
}
|
|
|
|
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
|
|
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
|
|
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
|
|
static inline void sync_throttle(struct task_group *tg, int cpu) {}
|
|
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
|
|
|
|
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline int throttled_lb_pair(struct task_group *tg,
|
|
int src_cpu, int dest_cpu)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
|
|
#endif
|
|
|
|
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
|
|
{
|
|
return NULL;
|
|
}
|
|
static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
|
|
static inline void update_runtime_enabled(struct rq *rq) {}
|
|
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
|
|
|
|
#endif /* CONFIG_CFS_BANDWIDTH */
|
|
|
|
/**************************************************
|
|
* CFS operations on tasks:
|
|
*/
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
SCHED_WARN_ON(task_rq(p) != rq);
|
|
|
|
if (rq->cfs.h_nr_running > 1) {
|
|
u64 slice = sched_slice(cfs_rq, se);
|
|
u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
|
|
s64 delta = slice - ran;
|
|
|
|
if (delta < 0) {
|
|
if (rq->curr == p)
|
|
resched_curr(rq);
|
|
return;
|
|
}
|
|
hrtick_start(rq, delta);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* called from enqueue/dequeue and updates the hrtick when the
|
|
* current task is from our class and nr_running is low enough
|
|
* to matter.
|
|
*/
|
|
static void hrtick_update(struct rq *rq)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
|
|
if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
|
|
return;
|
|
|
|
if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
|
|
hrtick_start_fair(rq, curr);
|
|
}
|
|
#else /* !CONFIG_SCHED_HRTICK */
|
|
static inline void
|
|
hrtick_start_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
}
|
|
|
|
static inline void hrtick_update(struct rq *rq)
|
|
{
|
|
}
|
|
#endif
|
|
|
|
#ifdef CONFIG_SMP
|
|
static inline unsigned long cpu_util(int cpu);
|
|
static unsigned long capacity_of(int cpu);
|
|
|
|
static inline bool cpu_overutilized(int cpu)
|
|
{
|
|
return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
|
|
}
|
|
|
|
static inline void update_overutilized_status(struct rq *rq)
|
|
{
|
|
if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu))
|
|
WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
|
|
}
|
|
#else
|
|
static inline void update_overutilized_status(struct rq *rq) { }
|
|
#endif
|
|
|
|
/*
|
|
* The enqueue_task method is called before nr_running is
|
|
* increased. Here we update the fair scheduling stats and
|
|
* then put the task into the rbtree:
|
|
*/
|
|
static void
|
|
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se;
|
|
|
|
/*
|
|
* The code below (indirectly) updates schedutil which looks at
|
|
* the cfs_rq utilization to select a frequency.
|
|
* Let's add the task's estimated utilization to the cfs_rq's
|
|
* estimated utilization, before we update schedutil.
|
|
*/
|
|
util_est_enqueue(&rq->cfs, p);
|
|
|
|
/*
|
|
* If in_iowait is set, the code below may not trigger any cpufreq
|
|
* utilization updates, so do it here explicitly with the IOWAIT flag
|
|
* passed.
|
|
*/
|
|
if (p->in_iowait)
|
|
cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
|
|
|
|
for_each_sched_entity(se) {
|
|
if (se->on_rq)
|
|
break;
|
|
cfs_rq = cfs_rq_of(se);
|
|
enqueue_entity(cfs_rq, se, flags);
|
|
|
|
/*
|
|
* end evaluation on encountering a throttled cfs_rq
|
|
*
|
|
* note: in the case of encountering a throttled cfs_rq we will
|
|
* post the final h_nr_running increment below.
|
|
*/
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
cfs_rq->h_nr_running++;
|
|
|
|
flags = ENQUEUE_WAKEUP;
|
|
}
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
cfs_rq->h_nr_running++;
|
|
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
|
|
update_load_avg(cfs_rq, se, UPDATE_TG);
|
|
update_cfs_group(se);
|
|
}
|
|
|
|
if (!se) {
|
|
add_nr_running(rq, 1);
|
|
/*
|
|
* Since new tasks are assigned an initial util_avg equal to
|
|
* half of the spare capacity of their CPU, tiny tasks have the
|
|
* ability to cross the overutilized threshold, which will
|
|
* result in the load balancer ruining all the task placement
|
|
* done by EAS. As a way to mitigate that effect, do not account
|
|
* for the first enqueue operation of new tasks during the
|
|
* overutilized flag detection.
|
|
*
|
|
* A better way of solving this problem would be to wait for
|
|
* the PELT signals of tasks to converge before taking them
|
|
* into account, but that is not straightforward to implement,
|
|
* and the following generally works well enough in practice.
|
|
*/
|
|
if (flags & ENQUEUE_WAKEUP)
|
|
update_overutilized_status(rq);
|
|
|
|
}
|
|
|
|
if (cfs_bandwidth_used()) {
|
|
/*
|
|
* When bandwidth control is enabled; the cfs_rq_throttled()
|
|
* breaks in the above iteration can result in incomplete
|
|
* leaf list maintenance, resulting in triggering the assertion
|
|
* below.
|
|
*/
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
|
|
if (list_add_leaf_cfs_rq(cfs_rq))
|
|
break;
|
|
}
|
|
}
|
|
|
|
assert_list_leaf_cfs_rq(rq);
|
|
|
|
hrtick_update(rq);
|
|
}
|
|
|
|
static void set_next_buddy(struct sched_entity *se);
|
|
|
|
/*
|
|
* The dequeue_task method is called before nr_running is
|
|
* decreased. We remove the task from the rbtree and
|
|
* update the fair scheduling stats:
|
|
*/
|
|
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se;
|
|
int task_sleep = flags & DEQUEUE_SLEEP;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
dequeue_entity(cfs_rq, se, flags);
|
|
|
|
/*
|
|
* end evaluation on encountering a throttled cfs_rq
|
|
*
|
|
* note: in the case of encountering a throttled cfs_rq we will
|
|
* post the final h_nr_running decrement below.
|
|
*/
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
cfs_rq->h_nr_running--;
|
|
|
|
/* Don't dequeue parent if it has other entities besides us */
|
|
if (cfs_rq->load.weight) {
|
|
/* Avoid re-evaluating load for this entity: */
|
|
se = parent_entity(se);
|
|
/*
|
|
* Bias pick_next to pick a task from this cfs_rq, as
|
|
* p is sleeping when it is within its sched_slice.
|
|
*/
|
|
if (task_sleep && se && !throttled_hierarchy(cfs_rq))
|
|
set_next_buddy(se);
|
|
break;
|
|
}
|
|
flags |= DEQUEUE_SLEEP;
|
|
}
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
cfs_rq->h_nr_running--;
|
|
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
|
|
update_load_avg(cfs_rq, se, UPDATE_TG);
|
|
update_cfs_group(se);
|
|
}
|
|
|
|
if (!se)
|
|
sub_nr_running(rq, 1);
|
|
|
|
util_est_dequeue(&rq->cfs, p, task_sleep);
|
|
hrtick_update(rq);
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
/* Working cpumask for: load_balance, load_balance_newidle. */
|
|
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
|
|
DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
/*
|
|
* per rq 'load' arrray crap; XXX kill this.
|
|
*/
|
|
|
|
/*
|
|
* The exact cpuload calculated at every tick would be:
|
|
*
|
|
* load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
|
|
*
|
|
* If a CPU misses updates for n ticks (as it was idle) and update gets
|
|
* called on the n+1-th tick when CPU may be busy, then we have:
|
|
*
|
|
* load_n = (1 - 1/2^i)^n * load_0
|
|
* load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
|
|
*
|
|
* decay_load_missed() below does efficient calculation of
|
|
*
|
|
* load' = (1 - 1/2^i)^n * load
|
|
*
|
|
* Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
|
|
* This allows us to precompute the above in said factors, thereby allowing the
|
|
* reduction of an arbitrary n in O(log_2 n) steps. (See also
|
|
* fixed_power_int())
|
|
*
|
|
* The calculation is approximated on a 128 point scale.
|
|
*/
|
|
#define DEGRADE_SHIFT 7
|
|
|
|
static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
|
|
static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
|
|
{ 0, 0, 0, 0, 0, 0, 0, 0 },
|
|
{ 64, 32, 8, 0, 0, 0, 0, 0 },
|
|
{ 96, 72, 40, 12, 1, 0, 0, 0 },
|
|
{ 112, 98, 75, 43, 15, 1, 0, 0 },
|
|
{ 120, 112, 98, 76, 45, 16, 2, 0 }
|
|
};
|
|
|
|
/*
|
|
* Update cpu_load for any missed ticks, due to tickless idle. The backlog
|
|
* would be when CPU is idle and so we just decay the old load without
|
|
* adding any new load.
|
|
*/
|
|
static unsigned long
|
|
decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
|
|
{
|
|
int j = 0;
|
|
|
|
if (!missed_updates)
|
|
return load;
|
|
|
|
if (missed_updates >= degrade_zero_ticks[idx])
|
|
return 0;
|
|
|
|
if (idx == 1)
|
|
return load >> missed_updates;
|
|
|
|
while (missed_updates) {
|
|
if (missed_updates % 2)
|
|
load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
|
|
|
|
missed_updates >>= 1;
|
|
j++;
|
|
}
|
|
return load;
|
|
}
|
|
|
|
static struct {
|
|
cpumask_var_t idle_cpus_mask;
|
|
atomic_t nr_cpus;
|
|
int has_blocked; /* Idle CPUS has blocked load */
|
|
unsigned long next_balance; /* in jiffy units */
|
|
unsigned long next_blocked; /* Next update of blocked load in jiffies */
|
|
} nohz ____cacheline_aligned;
|
|
|
|
#endif /* CONFIG_NO_HZ_COMMON */
|
|
|
|
/**
|
|
* __cpu_load_update - update the rq->cpu_load[] statistics
|
|
* @this_rq: The rq to update statistics for
|
|
* @this_load: The current load
|
|
* @pending_updates: The number of missed updates
|
|
*
|
|
* Update rq->cpu_load[] statistics. This function is usually called every
|
|
* scheduler tick (TICK_NSEC).
|
|
*
|
|
* This function computes a decaying average:
|
|
*
|
|
* load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
|
|
*
|
|
* Because of NOHZ it might not get called on every tick which gives need for
|
|
* the @pending_updates argument.
|
|
*
|
|
* load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
|
|
* = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
|
|
* = A * (A * load[i]_n-2 + B) + B
|
|
* = A * (A * (A * load[i]_n-3 + B) + B) + B
|
|
* = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
|
|
* = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
|
|
* = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
|
|
* = (1 - 1/2^i)^n * (load[i]_0 - load) + load
|
|
*
|
|
* In the above we've assumed load_n := load, which is true for NOHZ_FULL as
|
|
* any change in load would have resulted in the tick being turned back on.
|
|
*
|
|
* For regular NOHZ, this reduces to:
|
|
*
|
|
* load[i]_n = (1 - 1/2^i)^n * load[i]_0
|
|
*
|
|
* see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
|
|
* term.
|
|
*/
|
|
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
|
|
unsigned long pending_updates)
|
|
{
|
|
unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
|
|
int i, scale;
|
|
|
|
this_rq->nr_load_updates++;
|
|
|
|
/* Update our load: */
|
|
this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
|
|
for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
|
|
unsigned long old_load, new_load;
|
|
|
|
/* scale is effectively 1 << i now, and >> i divides by scale */
|
|
|
|
old_load = this_rq->cpu_load[i];
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
old_load = decay_load_missed(old_load, pending_updates - 1, i);
|
|
if (tickless_load) {
|
|
old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
|
|
/*
|
|
* old_load can never be a negative value because a
|
|
* decayed tickless_load cannot be greater than the
|
|
* original tickless_load.
|
|
*/
|
|
old_load += tickless_load;
|
|
}
|
|
#endif
|
|
new_load = this_load;
|
|
/*
|
|
* Round up the averaging division if load is increasing. This
|
|
* prevents us from getting stuck on 9 if the load is 10, for
|
|
* example.
|
|
*/
|
|
if (new_load > old_load)
|
|
new_load += scale - 1;
|
|
|
|
this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
|
|
}
|
|
}
|
|
|
|
/* Used instead of source_load when we know the type == 0 */
|
|
static unsigned long weighted_cpuload(struct rq *rq)
|
|
{
|
|
return cfs_rq_runnable_load_avg(&rq->cfs);
|
|
}
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
/*
|
|
* There is no sane way to deal with nohz on smp when using jiffies because the
|
|
* CPU doing the jiffies update might drift wrt the CPU doing the jiffy reading
|
|
* causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
|
|
*
|
|
* Therefore we need to avoid the delta approach from the regular tick when
|
|
* possible since that would seriously skew the load calculation. This is why we
|
|
* use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
|
|
* jiffies deltas for updates happening while in nohz mode (idle ticks, idle
|
|
* loop exit, nohz_idle_balance, nohz full exit...)
|
|
*
|
|
* This means we might still be one tick off for nohz periods.
|
|
*/
|
|
|
|
static void cpu_load_update_nohz(struct rq *this_rq,
|
|
unsigned long curr_jiffies,
|
|
unsigned long load)
|
|
{
|
|
unsigned long pending_updates;
|
|
|
|
pending_updates = curr_jiffies - this_rq->last_load_update_tick;
|
|
if (pending_updates) {
|
|
this_rq->last_load_update_tick = curr_jiffies;
|
|
/*
|
|
* In the regular NOHZ case, we were idle, this means load 0.
|
|
* In the NOHZ_FULL case, we were non-idle, we should consider
|
|
* its weighted load.
|
|
*/
|
|
cpu_load_update(this_rq, load, pending_updates);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Called from nohz_idle_balance() to update the load ratings before doing the
|
|
* idle balance.
|
|
*/
|
|
static void cpu_load_update_idle(struct rq *this_rq)
|
|
{
|
|
/*
|
|
* bail if there's load or we're actually up-to-date.
|
|
*/
|
|
if (weighted_cpuload(this_rq))
|
|
return;
|
|
|
|
cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
|
|
}
|
|
|
|
/*
|
|
* Record CPU load on nohz entry so we know the tickless load to account
|
|
* on nohz exit. cpu_load[0] happens then to be updated more frequently
|
|
* than other cpu_load[idx] but it should be fine as cpu_load readers
|
|
* shouldn't rely into synchronized cpu_load[*] updates.
|
|
*/
|
|
void cpu_load_update_nohz_start(void)
|
|
{
|
|
struct rq *this_rq = this_rq();
|
|
|
|
/*
|
|
* This is all lockless but should be fine. If weighted_cpuload changes
|
|
* concurrently we'll exit nohz. And cpu_load write can race with
|
|
* cpu_load_update_idle() but both updater would be writing the same.
|
|
*/
|
|
this_rq->cpu_load[0] = weighted_cpuload(this_rq);
|
|
}
|
|
|
|
/*
|
|
* Account the tickless load in the end of a nohz frame.
|
|
*/
|
|
void cpu_load_update_nohz_stop(void)
|
|
{
|
|
unsigned long curr_jiffies = READ_ONCE(jiffies);
|
|
struct rq *this_rq = this_rq();
|
|
unsigned long load;
|
|
struct rq_flags rf;
|
|
|
|
if (curr_jiffies == this_rq->last_load_update_tick)
|
|
return;
|
|
|
|
load = weighted_cpuload(this_rq);
|
|
rq_lock(this_rq, &rf);
|
|
update_rq_clock(this_rq);
|
|
cpu_load_update_nohz(this_rq, curr_jiffies, load);
|
|
rq_unlock(this_rq, &rf);
|
|
}
|
|
#else /* !CONFIG_NO_HZ_COMMON */
|
|
static inline void cpu_load_update_nohz(struct rq *this_rq,
|
|
unsigned long curr_jiffies,
|
|
unsigned long load) { }
|
|
#endif /* CONFIG_NO_HZ_COMMON */
|
|
|
|
static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
|
|
{
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
/* See the mess around cpu_load_update_nohz(). */
|
|
this_rq->last_load_update_tick = READ_ONCE(jiffies);
|
|
#endif
|
|
cpu_load_update(this_rq, load, 1);
|
|
}
|
|
|
|
/*
|
|
* Called from scheduler_tick()
|
|
*/
|
|
void cpu_load_update_active(struct rq *this_rq)
|
|
{
|
|
unsigned long load = weighted_cpuload(this_rq);
|
|
|
|
if (tick_nohz_tick_stopped())
|
|
cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
|
|
else
|
|
cpu_load_update_periodic(this_rq, load);
|
|
}
|
|
|
|
/*
|
|
* Return a low guess at the load of a migration-source CPU weighted
|
|
* according to the scheduling class and "nice" value.
|
|
*
|
|
* We want to under-estimate the load of migration sources, to
|
|
* balance conservatively.
|
|
*/
|
|
static unsigned long source_load(int cpu, int type)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long total = weighted_cpuload(rq);
|
|
|
|
if (type == 0 || !sched_feat(LB_BIAS))
|
|
return total;
|
|
|
|
return min(rq->cpu_load[type-1], total);
|
|
}
|
|
|
|
/*
|
|
* Return a high guess at the load of a migration-target CPU weighted
|
|
* according to the scheduling class and "nice" value.
|
|
*/
|
|
static unsigned long target_load(int cpu, int type)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long total = weighted_cpuload(rq);
|
|
|
|
if (type == 0 || !sched_feat(LB_BIAS))
|
|
return total;
|
|
|
|
return max(rq->cpu_load[type-1], total);
|
|
}
|
|
|
|
static unsigned long capacity_of(int cpu)
|
|
{
|
|
return cpu_rq(cpu)->cpu_capacity;
|
|
}
|
|
|
|
static unsigned long cpu_avg_load_per_task(int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
|
|
unsigned long load_avg = weighted_cpuload(rq);
|
|
|
|
if (nr_running)
|
|
return load_avg / nr_running;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void record_wakee(struct task_struct *p)
|
|
{
|
|
/*
|
|
* Only decay a single time; tasks that have less then 1 wakeup per
|
|
* jiffy will not have built up many flips.
|
|
*/
|
|
if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
|
|
current->wakee_flips >>= 1;
|
|
current->wakee_flip_decay_ts = jiffies;
|
|
}
|
|
|
|
if (current->last_wakee != p) {
|
|
current->last_wakee = p;
|
|
current->wakee_flips++;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Detect M:N waker/wakee relationships via a switching-frequency heuristic.
|
|
*
|
|
* A waker of many should wake a different task than the one last awakened
|
|
* at a frequency roughly N times higher than one of its wakees.
|
|
*
|
|
* In order to determine whether we should let the load spread vs consolidating
|
|
* to shared cache, we look for a minimum 'flip' frequency of llc_size in one
|
|
* partner, and a factor of lls_size higher frequency in the other.
|
|
*
|
|
* With both conditions met, we can be relatively sure that the relationship is
|
|
* non-monogamous, with partner count exceeding socket size.
|
|
*
|
|
* Waker/wakee being client/server, worker/dispatcher, interrupt source or
|
|
* whatever is irrelevant, spread criteria is apparent partner count exceeds
|
|
* socket size.
|
|
*/
|
|
static int wake_wide(struct task_struct *p)
|
|
{
|
|
unsigned int master = current->wakee_flips;
|
|
unsigned int slave = p->wakee_flips;
|
|
int factor = this_cpu_read(sd_llc_size);
|
|
|
|
if (master < slave)
|
|
swap(master, slave);
|
|
if (slave < factor || master < slave * factor)
|
|
return 0;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* The purpose of wake_affine() is to quickly determine on which CPU we can run
|
|
* soonest. For the purpose of speed we only consider the waking and previous
|
|
* CPU.
|
|
*
|
|
* wake_affine_idle() - only considers 'now', it check if the waking CPU is
|
|
* cache-affine and is (or will be) idle.
|
|
*
|
|
* wake_affine_weight() - considers the weight to reflect the average
|
|
* scheduling latency of the CPUs. This seems to work
|
|
* for the overloaded case.
|
|
*/
|
|
static int
|
|
wake_affine_idle(int this_cpu, int prev_cpu, int sync)
|
|
{
|
|
/*
|
|
* If this_cpu is idle, it implies the wakeup is from interrupt
|
|
* context. Only allow the move if cache is shared. Otherwise an
|
|
* interrupt intensive workload could force all tasks onto one
|
|
* node depending on the IO topology or IRQ affinity settings.
|
|
*
|
|
* If the prev_cpu is idle and cache affine then avoid a migration.
|
|
* There is no guarantee that the cache hot data from an interrupt
|
|
* is more important than cache hot data on the prev_cpu and from
|
|
* a cpufreq perspective, it's better to have higher utilisation
|
|
* on one CPU.
|
|
*/
|
|
if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
|
|
return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
|
|
|
|
if (sync && cpu_rq(this_cpu)->nr_running == 1)
|
|
return this_cpu;
|
|
|
|
return nr_cpumask_bits;
|
|
}
|
|
|
|
static int
|
|
wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
|
|
int this_cpu, int prev_cpu, int sync)
|
|
{
|
|
s64 this_eff_load, prev_eff_load;
|
|
unsigned long task_load;
|
|
|
|
this_eff_load = target_load(this_cpu, sd->wake_idx);
|
|
|
|
if (sync) {
|
|
unsigned long current_load = task_h_load(current);
|
|
|
|
if (current_load > this_eff_load)
|
|
return this_cpu;
|
|
|
|
this_eff_load -= current_load;
|
|
}
|
|
|
|
task_load = task_h_load(p);
|
|
|
|
this_eff_load += task_load;
|
|
if (sched_feat(WA_BIAS))
|
|
this_eff_load *= 100;
|
|
this_eff_load *= capacity_of(prev_cpu);
|
|
|
|
prev_eff_load = source_load(prev_cpu, sd->wake_idx);
|
|
prev_eff_load -= task_load;
|
|
if (sched_feat(WA_BIAS))
|
|
prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
|
|
prev_eff_load *= capacity_of(this_cpu);
|
|
|
|
/*
|
|
* If sync, adjust the weight of prev_eff_load such that if
|
|
* prev_eff == this_eff that select_idle_sibling() will consider
|
|
* stacking the wakee on top of the waker if no other CPU is
|
|
* idle.
|
|
*/
|
|
if (sync)
|
|
prev_eff_load += 1;
|
|
|
|
return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
|
|
}
|
|
|
|
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
|
|
int this_cpu, int prev_cpu, int sync)
|
|
{
|
|
int target = nr_cpumask_bits;
|
|
|
|
if (sched_feat(WA_IDLE))
|
|
target = wake_affine_idle(this_cpu, prev_cpu, sync);
|
|
|
|
if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
|
|
target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
|
|
|
|
schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
|
|
if (target == nr_cpumask_bits)
|
|
return prev_cpu;
|
|
|
|
schedstat_inc(sd->ttwu_move_affine);
|
|
schedstat_inc(p->se.statistics.nr_wakeups_affine);
|
|
return target;
|
|
}
|
|
|
|
static unsigned long cpu_util_without(int cpu, struct task_struct *p);
|
|
|
|
static unsigned long capacity_spare_without(int cpu, struct task_struct *p)
|
|
{
|
|
return max_t(long, capacity_of(cpu) - cpu_util_without(cpu, p), 0);
|
|
}
|
|
|
|
/*
|
|
* find_idlest_group finds and returns the least busy CPU group within the
|
|
* domain.
|
|
*
|
|
* Assumes p is allowed on at least one CPU in sd.
|
|
*/
|
|
static struct sched_group *
|
|
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
|
|
int this_cpu, int sd_flag)
|
|
{
|
|
struct sched_group *idlest = NULL, *group = sd->groups;
|
|
struct sched_group *most_spare_sg = NULL;
|
|
unsigned long min_runnable_load = ULONG_MAX;
|
|
unsigned long this_runnable_load = ULONG_MAX;
|
|
unsigned long min_avg_load = ULONG_MAX, this_avg_load = ULONG_MAX;
|
|
unsigned long most_spare = 0, this_spare = 0;
|
|
int load_idx = sd->forkexec_idx;
|
|
int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
|
|
unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
|
|
(sd->imbalance_pct-100) / 100;
|
|
|
|
if (sd_flag & SD_BALANCE_WAKE)
|
|
load_idx = sd->wake_idx;
|
|
|
|
do {
|
|
unsigned long load, avg_load, runnable_load;
|
|
unsigned long spare_cap, max_spare_cap;
|
|
int local_group;
|
|
int i;
|
|
|
|
/* Skip over this group if it has no CPUs allowed */
|
|
if (!cpumask_intersects(sched_group_span(group),
|
|
&p->cpus_allowed))
|
|
continue;
|
|
|
|
local_group = cpumask_test_cpu(this_cpu,
|
|
sched_group_span(group));
|
|
|
|
/*
|
|
* Tally up the load of all CPUs in the group and find
|
|
* the group containing the CPU with most spare capacity.
|
|
*/
|
|
avg_load = 0;
|
|
runnable_load = 0;
|
|
max_spare_cap = 0;
|
|
|
|
for_each_cpu(i, sched_group_span(group)) {
|
|
/* Bias balancing toward CPUs of our domain */
|
|
if (local_group)
|
|
load = source_load(i, load_idx);
|
|
else
|
|
load = target_load(i, load_idx);
|
|
|
|
runnable_load += load;
|
|
|
|
avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
|
|
|
|
spare_cap = capacity_spare_without(i, p);
|
|
|
|
if (spare_cap > max_spare_cap)
|
|
max_spare_cap = spare_cap;
|
|
}
|
|
|
|
/* Adjust by relative CPU capacity of the group */
|
|
avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
|
|
group->sgc->capacity;
|
|
runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
|
|
group->sgc->capacity;
|
|
|
|
if (local_group) {
|
|
this_runnable_load = runnable_load;
|
|
this_avg_load = avg_load;
|
|
this_spare = max_spare_cap;
|
|
} else {
|
|
if (min_runnable_load > (runnable_load + imbalance)) {
|
|
/*
|
|
* The runnable load is significantly smaller
|
|
* so we can pick this new CPU:
|
|
*/
|
|
min_runnable_load = runnable_load;
|
|
min_avg_load = avg_load;
|
|
idlest = group;
|
|
} else if ((runnable_load < (min_runnable_load + imbalance)) &&
|
|
(100*min_avg_load > imbalance_scale*avg_load)) {
|
|
/*
|
|
* The runnable loads are close so take the
|
|
* blocked load into account through avg_load:
|
|
*/
|
|
min_avg_load = avg_load;
|
|
idlest = group;
|
|
}
|
|
|
|
if (most_spare < max_spare_cap) {
|
|
most_spare = max_spare_cap;
|
|
most_spare_sg = group;
|
|
}
|
|
}
|
|
} while (group = group->next, group != sd->groups);
|
|
|
|
/*
|
|
* The cross-over point between using spare capacity or least load
|
|
* is too conservative for high utilization tasks on partially
|
|
* utilized systems if we require spare_capacity > task_util(p),
|
|
* so we allow for some task stuffing by using
|
|
* spare_capacity > task_util(p)/2.
|
|
*
|
|
* Spare capacity can't be used for fork because the utilization has
|
|
* not been set yet, we must first select a rq to compute the initial
|
|
* utilization.
|
|
*/
|
|
if (sd_flag & SD_BALANCE_FORK)
|
|
goto skip_spare;
|
|
|
|
if (this_spare > task_util(p) / 2 &&
|
|
imbalance_scale*this_spare > 100*most_spare)
|
|
return NULL;
|
|
|
|
if (most_spare > task_util(p) / 2)
|
|
return most_spare_sg;
|
|
|
|
skip_spare:
|
|
if (!idlest)
|
|
return NULL;
|
|
|
|
/*
|
|
* When comparing groups across NUMA domains, it's possible for the
|
|
* local domain to be very lightly loaded relative to the remote
|
|
* domains but "imbalance" skews the comparison making remote CPUs
|
|
* look much more favourable. When considering cross-domain, add
|
|
* imbalance to the runnable load on the remote node and consider
|
|
* staying local.
|
|
*/
|
|
if ((sd->flags & SD_NUMA) &&
|
|
min_runnable_load + imbalance >= this_runnable_load)
|
|
return NULL;
|
|
|
|
if (min_runnable_load > (this_runnable_load + imbalance))
|
|
return NULL;
|
|
|
|
if ((this_runnable_load < (min_runnable_load + imbalance)) &&
|
|
(100*this_avg_load < imbalance_scale*min_avg_load))
|
|
return NULL;
|
|
|
|
return idlest;
|
|
}
|
|
|
|
/*
|
|
* find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
|
|
*/
|
|
static int
|
|
find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
|
|
{
|
|
unsigned long load, min_load = ULONG_MAX;
|
|
unsigned int min_exit_latency = UINT_MAX;
|
|
u64 latest_idle_timestamp = 0;
|
|
int least_loaded_cpu = this_cpu;
|
|
int shallowest_idle_cpu = -1;
|
|
int i;
|
|
|
|
/* Check if we have any choice: */
|
|
if (group->group_weight == 1)
|
|
return cpumask_first(sched_group_span(group));
|
|
|
|
/* Traverse only the allowed CPUs */
|
|
for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
|
|
if (available_idle_cpu(i)) {
|
|
struct rq *rq = cpu_rq(i);
|
|
struct cpuidle_state *idle = idle_get_state(rq);
|
|
if (idle && idle->exit_latency < min_exit_latency) {
|
|
/*
|
|
* We give priority to a CPU whose idle state
|
|
* has the smallest exit latency irrespective
|
|
* of any idle timestamp.
|
|
*/
|
|
min_exit_latency = idle->exit_latency;
|
|
latest_idle_timestamp = rq->idle_stamp;
|
|
shallowest_idle_cpu = i;
|
|
} else if ((!idle || idle->exit_latency == min_exit_latency) &&
|
|
rq->idle_stamp > latest_idle_timestamp) {
|
|
/*
|
|
* If equal or no active idle state, then
|
|
* the most recently idled CPU might have
|
|
* a warmer cache.
|
|
*/
|
|
latest_idle_timestamp = rq->idle_stamp;
|
|
shallowest_idle_cpu = i;
|
|
}
|
|
} else if (shallowest_idle_cpu == -1) {
|
|
load = weighted_cpuload(cpu_rq(i));
|
|
if (load < min_load) {
|
|
min_load = load;
|
|
least_loaded_cpu = i;
|
|
}
|
|
}
|
|
}
|
|
|
|
return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
|
|
}
|
|
|
|
static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
|
|
int cpu, int prev_cpu, int sd_flag)
|
|
{
|
|
int new_cpu = cpu;
|
|
|
|
if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
|
|
return prev_cpu;
|
|
|
|
/*
|
|
* We need task's util for capacity_spare_without, sync it up to
|
|
* prev_cpu's last_update_time.
|
|
*/
|
|
if (!(sd_flag & SD_BALANCE_FORK))
|
|
sync_entity_load_avg(&p->se);
|
|
|
|
while (sd) {
|
|
struct sched_group *group;
|
|
struct sched_domain *tmp;
|
|
int weight;
|
|
|
|
if (!(sd->flags & sd_flag)) {
|
|
sd = sd->child;
|
|
continue;
|
|
}
|
|
|
|
group = find_idlest_group(sd, p, cpu, sd_flag);
|
|
if (!group) {
|
|
sd = sd->child;
|
|
continue;
|
|
}
|
|
|
|
new_cpu = find_idlest_group_cpu(group, p, cpu);
|
|
if (new_cpu == cpu) {
|
|
/* Now try balancing at a lower domain level of 'cpu': */
|
|
sd = sd->child;
|
|
continue;
|
|
}
|
|
|
|
/* Now try balancing at a lower domain level of 'new_cpu': */
|
|
cpu = new_cpu;
|
|
weight = sd->span_weight;
|
|
sd = NULL;
|
|
for_each_domain(cpu, tmp) {
|
|
if (weight <= tmp->span_weight)
|
|
break;
|
|
if (tmp->flags & sd_flag)
|
|
sd = tmp;
|
|
}
|
|
}
|
|
|
|
return new_cpu;
|
|
}
|
|
|
|
#ifdef CONFIG_SCHED_SMT
|
|
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
|
|
EXPORT_SYMBOL_GPL(sched_smt_present);
|
|
|
|
static inline void set_idle_cores(int cpu, int val)
|
|
{
|
|
struct sched_domain_shared *sds;
|
|
|
|
sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
|
|
if (sds)
|
|
WRITE_ONCE(sds->has_idle_cores, val);
|
|
}
|
|
|
|
static inline bool test_idle_cores(int cpu, bool def)
|
|
{
|
|
struct sched_domain_shared *sds;
|
|
|
|
sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
|
|
if (sds)
|
|
return READ_ONCE(sds->has_idle_cores);
|
|
|
|
return def;
|
|
}
|
|
|
|
/*
|
|
* Scans the local SMT mask to see if the entire core is idle, and records this
|
|
* information in sd_llc_shared->has_idle_cores.
|
|
*
|
|
* Since SMT siblings share all cache levels, inspecting this limited remote
|
|
* state should be fairly cheap.
|
|
*/
|
|
void __update_idle_core(struct rq *rq)
|
|
{
|
|
int core = cpu_of(rq);
|
|
int cpu;
|
|
|
|
rcu_read_lock();
|
|
if (test_idle_cores(core, true))
|
|
goto unlock;
|
|
|
|
for_each_cpu(cpu, cpu_smt_mask(core)) {
|
|
if (cpu == core)
|
|
continue;
|
|
|
|
if (!available_idle_cpu(cpu))
|
|
goto unlock;
|
|
}
|
|
|
|
set_idle_cores(core, 1);
|
|
unlock:
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/*
|
|
* Scan the entire LLC domain for idle cores; this dynamically switches off if
|
|
* there are no idle cores left in the system; tracked through
|
|
* sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
|
|
*/
|
|
static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
|
|
{
|
|
struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
|
|
int core, cpu;
|
|
|
|
if (!static_branch_likely(&sched_smt_present))
|
|
return -1;
|
|
|
|
if (!test_idle_cores(target, false))
|
|
return -1;
|
|
|
|
cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
|
|
|
|
for_each_cpu_wrap(core, cpus, target) {
|
|
bool idle = true;
|
|
|
|
for_each_cpu(cpu, cpu_smt_mask(core)) {
|
|
__cpumask_clear_cpu(cpu, cpus);
|
|
if (!available_idle_cpu(cpu))
|
|
idle = false;
|
|
}
|
|
|
|
if (idle)
|
|
return core;
|
|
}
|
|
|
|
/*
|
|
* Failed to find an idle core; stop looking for one.
|
|
*/
|
|
set_idle_cores(target, 0);
|
|
|
|
return -1;
|
|
}
|
|
|
|
/*
|
|
* Scan the local SMT mask for idle CPUs.
|
|
*/
|
|
static int select_idle_smt(struct task_struct *p, int target)
|
|
{
|
|
int cpu;
|
|
|
|
if (!static_branch_likely(&sched_smt_present))
|
|
return -1;
|
|
|
|
for_each_cpu(cpu, cpu_smt_mask(target)) {
|
|
if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
|
|
continue;
|
|
if (available_idle_cpu(cpu))
|
|
return cpu;
|
|
}
|
|
|
|
return -1;
|
|
}
|
|
|
|
#else /* CONFIG_SCHED_SMT */
|
|
|
|
static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
|
|
{
|
|
return -1;
|
|
}
|
|
|
|
static inline int select_idle_smt(struct task_struct *p, int target)
|
|
{
|
|
return -1;
|
|
}
|
|
|
|
#endif /* CONFIG_SCHED_SMT */
|
|
|
|
/*
|
|
* Scan the LLC domain for idle CPUs; this is dynamically regulated by
|
|
* comparing the average scan cost (tracked in sd->avg_scan_cost) against the
|
|
* average idle time for this rq (as found in rq->avg_idle).
|
|
*/
|
|
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
|
|
{
|
|
struct sched_domain *this_sd;
|
|
u64 avg_cost, avg_idle;
|
|
u64 time, cost;
|
|
s64 delta;
|
|
int cpu, nr = INT_MAX;
|
|
|
|
this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
|
|
if (!this_sd)
|
|
return -1;
|
|
|
|
/*
|
|
* Due to large variance we need a large fuzz factor; hackbench in
|
|
* particularly is sensitive here.
|
|
*/
|
|
avg_idle = this_rq()->avg_idle / 512;
|
|
avg_cost = this_sd->avg_scan_cost + 1;
|
|
|
|
if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
|
|
return -1;
|
|
|
|
if (sched_feat(SIS_PROP)) {
|
|
u64 span_avg = sd->span_weight * avg_idle;
|
|
if (span_avg > 4*avg_cost)
|
|
nr = div_u64(span_avg, avg_cost);
|
|
else
|
|
nr = 4;
|
|
}
|
|
|
|
time = local_clock();
|
|
|
|
for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
|
|
if (!--nr)
|
|
return -1;
|
|
if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
|
|
continue;
|
|
if (available_idle_cpu(cpu))
|
|
break;
|
|
}
|
|
|
|
time = local_clock() - time;
|
|
cost = this_sd->avg_scan_cost;
|
|
delta = (s64)(time - cost) / 8;
|
|
this_sd->avg_scan_cost += delta;
|
|
|
|
return cpu;
|
|
}
|
|
|
|
/*
|
|
* Try and locate an idle core/thread in the LLC cache domain.
|
|
*/
|
|
static int select_idle_sibling(struct task_struct *p, int prev, int target)
|
|
{
|
|
struct sched_domain *sd;
|
|
int i, recent_used_cpu;
|
|
|
|
if (available_idle_cpu(target))
|
|
return target;
|
|
|
|
/*
|
|
* If the previous CPU is cache affine and idle, don't be stupid:
|
|
*/
|
|
if (prev != target && cpus_share_cache(prev, target) && available_idle_cpu(prev))
|
|
return prev;
|
|
|
|
/* Check a recently used CPU as a potential idle candidate: */
|
|
recent_used_cpu = p->recent_used_cpu;
|
|
if (recent_used_cpu != prev &&
|
|
recent_used_cpu != target &&
|
|
cpus_share_cache(recent_used_cpu, target) &&
|
|
available_idle_cpu(recent_used_cpu) &&
|
|
cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) {
|
|
/*
|
|
* Replace recent_used_cpu with prev as it is a potential
|
|
* candidate for the next wake:
|
|
*/
|
|
p->recent_used_cpu = prev;
|
|
return recent_used_cpu;
|
|
}
|
|
|
|
sd = rcu_dereference(per_cpu(sd_llc, target));
|
|
if (!sd)
|
|
return target;
|
|
|
|
i = select_idle_core(p, sd, target);
|
|
if ((unsigned)i < nr_cpumask_bits)
|
|
return i;
|
|
|
|
i = select_idle_cpu(p, sd, target);
|
|
if ((unsigned)i < nr_cpumask_bits)
|
|
return i;
|
|
|
|
i = select_idle_smt(p, target);
|
|
if ((unsigned)i < nr_cpumask_bits)
|
|
return i;
|
|
|
|
return target;
|
|
}
|
|
|
|
/**
|
|
* Amount of capacity of a CPU that is (estimated to be) used by CFS tasks
|
|
* @cpu: the CPU to get the utilization of
|
|
*
|
|
* The unit of the return value must be the one of capacity so we can compare
|
|
* the utilization with the capacity of the CPU that is available for CFS task
|
|
* (ie cpu_capacity).
|
|
*
|
|
* cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
|
|
* recent utilization of currently non-runnable tasks on a CPU. It represents
|
|
* the amount of utilization of a CPU in the range [0..capacity_orig] where
|
|
* capacity_orig is the cpu_capacity available at the highest frequency
|
|
* (arch_scale_freq_capacity()).
|
|
* The utilization of a CPU converges towards a sum equal to or less than the
|
|
* current capacity (capacity_curr <= capacity_orig) of the CPU because it is
|
|
* the running time on this CPU scaled by capacity_curr.
|
|
*
|
|
* The estimated utilization of a CPU is defined to be the maximum between its
|
|
* cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
|
|
* currently RUNNABLE on that CPU.
|
|
* This allows to properly represent the expected utilization of a CPU which
|
|
* has just got a big task running since a long sleep period. At the same time
|
|
* however it preserves the benefits of the "blocked utilization" in
|
|
* describing the potential for other tasks waking up on the same CPU.
|
|
*
|
|
* Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
|
|
* higher than capacity_orig because of unfortunate rounding in
|
|
* cfs.avg.util_avg or just after migrating tasks and new task wakeups until
|
|
* the average stabilizes with the new running time. We need to check that the
|
|
* utilization stays within the range of [0..capacity_orig] and cap it if
|
|
* necessary. Without utilization capping, a group could be seen as overloaded
|
|
* (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
|
|
* available capacity. We allow utilization to overshoot capacity_curr (but not
|
|
* capacity_orig) as it useful for predicting the capacity required after task
|
|
* migrations (scheduler-driven DVFS).
|
|
*
|
|
* Return: the (estimated) utilization for the specified CPU
|
|
*/
|
|
static inline unsigned long cpu_util(int cpu)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
unsigned int util;
|
|
|
|
cfs_rq = &cpu_rq(cpu)->cfs;
|
|
util = READ_ONCE(cfs_rq->avg.util_avg);
|
|
|
|
if (sched_feat(UTIL_EST))
|
|
util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
|
|
|
|
return min_t(unsigned long, util, capacity_orig_of(cpu));
|
|
}
|
|
|
|
/*
|
|
* cpu_util_without: compute cpu utilization without any contributions from *p
|
|
* @cpu: the CPU which utilization is requested
|
|
* @p: the task which utilization should be discounted
|
|
*
|
|
* The utilization of a CPU is defined by the utilization of tasks currently
|
|
* enqueued on that CPU as well as tasks which are currently sleeping after an
|
|
* execution on that CPU.
|
|
*
|
|
* This method returns the utilization of the specified CPU by discounting the
|
|
* utilization of the specified task, whenever the task is currently
|
|
* contributing to the CPU utilization.
|
|
*/
|
|
static unsigned long cpu_util_without(int cpu, struct task_struct *p)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
unsigned int util;
|
|
|
|
/* Task has no contribution or is new */
|
|
if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
|
|
return cpu_util(cpu);
|
|
|
|
cfs_rq = &cpu_rq(cpu)->cfs;
|
|
util = READ_ONCE(cfs_rq->avg.util_avg);
|
|
|
|
/* Discount task's util from CPU's util */
|
|
lsub_positive(&util, task_util(p));
|
|
|
|
/*
|
|
* Covered cases:
|
|
*
|
|
* a) if *p is the only task sleeping on this CPU, then:
|
|
* cpu_util (== task_util) > util_est (== 0)
|
|
* and thus we return:
|
|
* cpu_util_without = (cpu_util - task_util) = 0
|
|
*
|
|
* b) if other tasks are SLEEPING on this CPU, which is now exiting
|
|
* IDLE, then:
|
|
* cpu_util >= task_util
|
|
* cpu_util > util_est (== 0)
|
|
* and thus we discount *p's blocked utilization to return:
|
|
* cpu_util_without = (cpu_util - task_util) >= 0
|
|
*
|
|
* c) if other tasks are RUNNABLE on that CPU and
|
|
* util_est > cpu_util
|
|
* then we use util_est since it returns a more restrictive
|
|
* estimation of the spare capacity on that CPU, by just
|
|
* considering the expected utilization of tasks already
|
|
* runnable on that CPU.
|
|
*
|
|
* Cases a) and b) are covered by the above code, while case c) is
|
|
* covered by the following code when estimated utilization is
|
|
* enabled.
|
|
*/
|
|
if (sched_feat(UTIL_EST)) {
|
|
unsigned int estimated =
|
|
READ_ONCE(cfs_rq->avg.util_est.enqueued);
|
|
|
|
/*
|
|
* Despite the following checks we still have a small window
|
|
* for a possible race, when an execl's select_task_rq_fair()
|
|
* races with LB's detach_task():
|
|
*
|
|
* detach_task()
|
|
* p->on_rq = TASK_ON_RQ_MIGRATING;
|
|
* ---------------------------------- A
|
|
* deactivate_task() \
|
|
* dequeue_task() + RaceTime
|
|
* util_est_dequeue() /
|
|
* ---------------------------------- B
|
|
*
|
|
* The additional check on "current == p" it's required to
|
|
* properly fix the execl regression and it helps in further
|
|
* reducing the chances for the above race.
|
|
*/
|
|
if (unlikely(task_on_rq_queued(p) || current == p))
|
|
lsub_positive(&estimated, _task_util_est(p));
|
|
|
|
util = max(util, estimated);
|
|
}
|
|
|
|
/*
|
|
* Utilization (estimated) can exceed the CPU capacity, thus let's
|
|
* clamp to the maximum CPU capacity to ensure consistency with
|
|
* the cpu_util call.
|
|
*/
|
|
return min_t(unsigned long, util, capacity_orig_of(cpu));
|
|
}
|
|
|
|
/*
|
|
* Disable WAKE_AFFINE in the case where task @p doesn't fit in the
|
|
* capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
|
|
*
|
|
* In that case WAKE_AFFINE doesn't make sense and we'll let
|
|
* BALANCE_WAKE sort things out.
|
|
*/
|
|
static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
|
|
{
|
|
long min_cap, max_cap;
|
|
|
|
if (!static_branch_unlikely(&sched_asym_cpucapacity))
|
|
return 0;
|
|
|
|
min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu));
|
|
max_cap = cpu_rq(cpu)->rd->max_cpu_capacity;
|
|
|
|
/* Minimum capacity is close to max, no need to abort wake_affine */
|
|
if (max_cap - min_cap < max_cap >> 3)
|
|
return 0;
|
|
|
|
/* Bring task utilization in sync with prev_cpu */
|
|
sync_entity_load_avg(&p->se);
|
|
|
|
return !task_fits_capacity(p, min_cap);
|
|
}
|
|
|
|
/*
|
|
* Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued)
|
|
* to @dst_cpu.
|
|
*/
|
|
static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
|
|
{
|
|
struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
|
|
unsigned long util_est, util = READ_ONCE(cfs_rq->avg.util_avg);
|
|
|
|
/*
|
|
* If @p migrates from @cpu to another, remove its contribution. Or,
|
|
* if @p migrates from another CPU to @cpu, add its contribution. In
|
|
* the other cases, @cpu is not impacted by the migration, so the
|
|
* util_avg should already be correct.
|
|
*/
|
|
if (task_cpu(p) == cpu && dst_cpu != cpu)
|
|
sub_positive(&util, task_util(p));
|
|
else if (task_cpu(p) != cpu && dst_cpu == cpu)
|
|
util += task_util(p);
|
|
|
|
if (sched_feat(UTIL_EST)) {
|
|
util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);
|
|
|
|
/*
|
|
* During wake-up, the task isn't enqueued yet and doesn't
|
|
* appear in the cfs_rq->avg.util_est.enqueued of any rq,
|
|
* so just add it (if needed) to "simulate" what will be
|
|
* cpu_util() after the task has been enqueued.
|
|
*/
|
|
if (dst_cpu == cpu)
|
|
util_est += _task_util_est(p);
|
|
|
|
util = max(util, util_est);
|
|
}
|
|
|
|
return min(util, capacity_orig_of(cpu));
|
|
}
|
|
|
|
/*
|
|
* compute_energy(): Estimates the energy that would be consumed if @p was
|
|
* migrated to @dst_cpu. compute_energy() predicts what will be the utilization
|
|
* landscape of the * CPUs after the task migration, and uses the Energy Model
|
|
* to compute what would be the energy if we decided to actually migrate that
|
|
* task.
|
|
*/
|
|
static long
|
|
compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
|
|
{
|
|
long util, max_util, sum_util, energy = 0;
|
|
int cpu;
|
|
|
|
for (; pd; pd = pd->next) {
|
|
max_util = sum_util = 0;
|
|
/*
|
|
* The capacity state of CPUs of the current rd can be driven by
|
|
* CPUs of another rd if they belong to the same performance
|
|
* domain. So, account for the utilization of these CPUs too
|
|
* by masking pd with cpu_online_mask instead of the rd span.
|
|
*
|
|
* If an entire performance domain is outside of the current rd,
|
|
* it will not appear in its pd list and will not be accounted
|
|
* by compute_energy().
|
|
*/
|
|
for_each_cpu_and(cpu, perf_domain_span(pd), cpu_online_mask) {
|
|
util = cpu_util_next(cpu, p, dst_cpu);
|
|
util = schedutil_energy_util(cpu, util);
|
|
max_util = max(util, max_util);
|
|
sum_util += util;
|
|
}
|
|
|
|
energy += em_pd_energy(pd->em_pd, max_util, sum_util);
|
|
}
|
|
|
|
return energy;
|
|
}
|
|
|
|
/*
|
|
* find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
|
|
* waking task. find_energy_efficient_cpu() looks for the CPU with maximum
|
|
* spare capacity in each performance domain and uses it as a potential
|
|
* candidate to execute the task. Then, it uses the Energy Model to figure
|
|
* out which of the CPU candidates is the most energy-efficient.
|
|
*
|
|
* The rationale for this heuristic is as follows. In a performance domain,
|
|
* all the most energy efficient CPU candidates (according to the Energy
|
|
* Model) are those for which we'll request a low frequency. When there are
|
|
* several CPUs for which the frequency request will be the same, we don't
|
|
* have enough data to break the tie between them, because the Energy Model
|
|
* only includes active power costs. With this model, if we assume that
|
|
* frequency requests follow utilization (e.g. using schedutil), the CPU with
|
|
* the maximum spare capacity in a performance domain is guaranteed to be among
|
|
* the best candidates of the performance domain.
|
|
*
|
|
* In practice, it could be preferable from an energy standpoint to pack
|
|
* small tasks on a CPU in order to let other CPUs go in deeper idle states,
|
|
* but that could also hurt our chances to go cluster idle, and we have no
|
|
* ways to tell with the current Energy Model if this is actually a good
|
|
* idea or not. So, find_energy_efficient_cpu() basically favors
|
|
* cluster-packing, and spreading inside a cluster. That should at least be
|
|
* a good thing for latency, and this is consistent with the idea that most
|
|
* of the energy savings of EAS come from the asymmetry of the system, and
|
|
* not so much from breaking the tie between identical CPUs. That's also the
|
|
* reason why EAS is enabled in the topology code only for systems where
|
|
* SD_ASYM_CPUCAPACITY is set.
|
|
*
|
|
* NOTE: Forkees are not accepted in the energy-aware wake-up path because
|
|
* they don't have any useful utilization data yet and it's not possible to
|
|
* forecast their impact on energy consumption. Consequently, they will be
|
|
* placed by find_idlest_cpu() on the least loaded CPU, which might turn out
|
|
* to be energy-inefficient in some use-cases. The alternative would be to
|
|
* bias new tasks towards specific types of CPUs first, or to try to infer
|
|
* their util_avg from the parent task, but those heuristics could hurt
|
|
* other use-cases too. So, until someone finds a better way to solve this,
|
|
* let's keep things simple by re-using the existing slow path.
|
|
*/
|
|
|
|
static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
|
|
{
|
|
unsigned long prev_energy = ULONG_MAX, best_energy = ULONG_MAX;
|
|
struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
|
|
int cpu, best_energy_cpu = prev_cpu;
|
|
struct perf_domain *head, *pd;
|
|
unsigned long cpu_cap, util;
|
|
struct sched_domain *sd;
|
|
|
|
rcu_read_lock();
|
|
pd = rcu_dereference(rd->pd);
|
|
if (!pd || READ_ONCE(rd->overutilized))
|
|
goto fail;
|
|
head = pd;
|
|
|
|
/*
|
|
* Energy-aware wake-up happens on the lowest sched_domain starting
|
|
* from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
|
|
*/
|
|
sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
|
|
while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
|
|
sd = sd->parent;
|
|
if (!sd)
|
|
goto fail;
|
|
|
|
sync_entity_load_avg(&p->se);
|
|
if (!task_util_est(p))
|
|
goto unlock;
|
|
|
|
for (; pd; pd = pd->next) {
|
|
unsigned long cur_energy, spare_cap, max_spare_cap = 0;
|
|
int max_spare_cap_cpu = -1;
|
|
|
|
for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) {
|
|
if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
|
|
continue;
|
|
|
|
/* Skip CPUs that will be overutilized. */
|
|
util = cpu_util_next(cpu, p, cpu);
|
|
cpu_cap = capacity_of(cpu);
|
|
if (cpu_cap * 1024 < util * capacity_margin)
|
|
continue;
|
|
|
|
/* Always use prev_cpu as a candidate. */
|
|
if (cpu == prev_cpu) {
|
|
prev_energy = compute_energy(p, prev_cpu, head);
|
|
best_energy = min(best_energy, prev_energy);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Find the CPU with the maximum spare capacity in
|
|
* the performance domain
|
|
*/
|
|
spare_cap = cpu_cap - util;
|
|
if (spare_cap > max_spare_cap) {
|
|
max_spare_cap = spare_cap;
|
|
max_spare_cap_cpu = cpu;
|
|
}
|
|
}
|
|
|
|
/* Evaluate the energy impact of using this CPU. */
|
|
if (max_spare_cap_cpu >= 0) {
|
|
cur_energy = compute_energy(p, max_spare_cap_cpu, head);
|
|
if (cur_energy < best_energy) {
|
|
best_energy = cur_energy;
|
|
best_energy_cpu = max_spare_cap_cpu;
|
|
}
|
|
}
|
|
}
|
|
unlock:
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* Pick the best CPU if prev_cpu cannot be used, or if it saves at
|
|
* least 6% of the energy used by prev_cpu.
|
|
*/
|
|
if (prev_energy == ULONG_MAX)
|
|
return best_energy_cpu;
|
|
|
|
if ((prev_energy - best_energy) > (prev_energy >> 4))
|
|
return best_energy_cpu;
|
|
|
|
return prev_cpu;
|
|
|
|
fail:
|
|
rcu_read_unlock();
|
|
|
|
return -1;
|
|
}
|
|
|
|
/*
|
|
* select_task_rq_fair: Select target runqueue for the waking task in domains
|
|
* that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
|
|
* SD_BALANCE_FORK, or SD_BALANCE_EXEC.
|
|
*
|
|
* Balances load by selecting the idlest CPU in the idlest group, or under
|
|
* certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
|
|
*
|
|
* Returns the target CPU number.
|
|
*
|
|
* preempt must be disabled.
|
|
*/
|
|
static int
|
|
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
|
|
{
|
|
struct sched_domain *tmp, *sd = NULL;
|
|
int cpu = smp_processor_id();
|
|
int new_cpu = prev_cpu;
|
|
int want_affine = 0;
|
|
int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
|
|
|
|
if (sd_flag & SD_BALANCE_WAKE) {
|
|
record_wakee(p);
|
|
|
|
if (sched_energy_enabled()) {
|
|
new_cpu = find_energy_efficient_cpu(p, prev_cpu);
|
|
if (new_cpu >= 0)
|
|
return new_cpu;
|
|
new_cpu = prev_cpu;
|
|
}
|
|
|
|
want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu) &&
|
|
cpumask_test_cpu(cpu, &p->cpus_allowed);
|
|
}
|
|
|
|
rcu_read_lock();
|
|
for_each_domain(cpu, tmp) {
|
|
if (!(tmp->flags & SD_LOAD_BALANCE))
|
|
break;
|
|
|
|
/*
|
|
* If both 'cpu' and 'prev_cpu' are part of this domain,
|
|
* cpu is a valid SD_WAKE_AFFINE target.
|
|
*/
|
|
if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
|
|
cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
|
|
if (cpu != prev_cpu)
|
|
new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
|
|
|
|
sd = NULL; /* Prefer wake_affine over balance flags */
|
|
break;
|
|
}
|
|
|
|
if (tmp->flags & sd_flag)
|
|
sd = tmp;
|
|
else if (!want_affine)
|
|
break;
|
|
}
|
|
|
|
if (unlikely(sd)) {
|
|
/* Slow path */
|
|
new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
|
|
} else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
|
|
/* Fast path */
|
|
|
|
new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
|
|
|
|
if (want_affine)
|
|
current->recent_used_cpu = cpu;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return new_cpu;
|
|
}
|
|
|
|
static void detach_entity_cfs_rq(struct sched_entity *se);
|
|
|
|
/*
|
|
* Called immediately before a task is migrated to a new CPU; task_cpu(p) and
|
|
* cfs_rq_of(p) references at time of call are still valid and identify the
|
|
* previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
|
|
*/
|
|
static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
|
|
{
|
|
/*
|
|
* As blocked tasks retain absolute vruntime the migration needs to
|
|
* deal with this by subtracting the old and adding the new
|
|
* min_vruntime -- the latter is done by enqueue_entity() when placing
|
|
* the task on the new runqueue.
|
|
*/
|
|
if (p->state == TASK_WAKING) {
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
u64 min_vruntime;
|
|
|
|
#ifndef CONFIG_64BIT
|
|
u64 min_vruntime_copy;
|
|
|
|
do {
|
|
min_vruntime_copy = cfs_rq->min_vruntime_copy;
|
|
smp_rmb();
|
|
min_vruntime = cfs_rq->min_vruntime;
|
|
} while (min_vruntime != min_vruntime_copy);
|
|
#else
|
|
min_vruntime = cfs_rq->min_vruntime;
|
|
#endif
|
|
|
|
se->vruntime -= min_vruntime;
|
|
}
|
|
|
|
if (p->on_rq == TASK_ON_RQ_MIGRATING) {
|
|
/*
|
|
* In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
|
|
* rq->lock and can modify state directly.
|
|
*/
|
|
lockdep_assert_held(&task_rq(p)->lock);
|
|
detach_entity_cfs_rq(&p->se);
|
|
|
|
} else {
|
|
/*
|
|
* We are supposed to update the task to "current" time, then
|
|
* its up to date and ready to go to new CPU/cfs_rq. But we
|
|
* have difficulty in getting what current time is, so simply
|
|
* throw away the out-of-date time. This will result in the
|
|
* wakee task is less decayed, but giving the wakee more load
|
|
* sounds not bad.
|
|
*/
|
|
remove_entity_load_avg(&p->se);
|
|
}
|
|
|
|
/* Tell new CPU we are migrated */
|
|
p->se.avg.last_update_time = 0;
|
|
|
|
/* We have migrated, no longer consider this task hot */
|
|
p->se.exec_start = 0;
|
|
|
|
update_scan_period(p, new_cpu);
|
|
}
|
|
|
|
static void task_dead_fair(struct task_struct *p)
|
|
{
|
|
remove_entity_load_avg(&p->se);
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
static unsigned long wakeup_gran(struct sched_entity *se)
|
|
{
|
|
unsigned long gran = sysctl_sched_wakeup_granularity;
|
|
|
|
/*
|
|
* Since its curr running now, convert the gran from real-time
|
|
* to virtual-time in his units.
|
|
*
|
|
* By using 'se' instead of 'curr' we penalize light tasks, so
|
|
* they get preempted easier. That is, if 'se' < 'curr' then
|
|
* the resulting gran will be larger, therefore penalizing the
|
|
* lighter, if otoh 'se' > 'curr' then the resulting gran will
|
|
* be smaller, again penalizing the lighter task.
|
|
*
|
|
* This is especially important for buddies when the leftmost
|
|
* task is higher priority than the buddy.
|
|
*/
|
|
return calc_delta_fair(gran, se);
|
|
}
|
|
|
|
/*
|
|
* Should 'se' preempt 'curr'.
|
|
*
|
|
* |s1
|
|
* |s2
|
|
* |s3
|
|
* g
|
|
* |<--->|c
|
|
*
|
|
* w(c, s1) = -1
|
|
* w(c, s2) = 0
|
|
* w(c, s3) = 1
|
|
*
|
|
*/
|
|
static int
|
|
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
|
|
{
|
|
s64 gran, vdiff = curr->vruntime - se->vruntime;
|
|
|
|
if (vdiff <= 0)
|
|
return -1;
|
|
|
|
gran = wakeup_gran(se);
|
|
if (vdiff > gran)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void set_last_buddy(struct sched_entity *se)
|
|
{
|
|
if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
|
|
return;
|
|
|
|
for_each_sched_entity(se) {
|
|
if (SCHED_WARN_ON(!se->on_rq))
|
|
return;
|
|
cfs_rq_of(se)->last = se;
|
|
}
|
|
}
|
|
|
|
static void set_next_buddy(struct sched_entity *se)
|
|
{
|
|
if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
|
|
return;
|
|
|
|
for_each_sched_entity(se) {
|
|
if (SCHED_WARN_ON(!se->on_rq))
|
|
return;
|
|
cfs_rq_of(se)->next = se;
|
|
}
|
|
}
|
|
|
|
static void set_skip_buddy(struct sched_entity *se)
|
|
{
|
|
for_each_sched_entity(se)
|
|
cfs_rq_of(se)->skip = se;
|
|
}
|
|
|
|
/*
|
|
* Preempt the current task with a newly woken task if needed:
|
|
*/
|
|
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct sched_entity *se = &curr->se, *pse = &p->se;
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
|
int scale = cfs_rq->nr_running >= sched_nr_latency;
|
|
int next_buddy_marked = 0;
|
|
|
|
if (unlikely(se == pse))
|
|
return;
|
|
|
|
/*
|
|
* This is possible from callers such as attach_tasks(), in which we
|
|
* unconditionally check_prempt_curr() after an enqueue (which may have
|
|
* lead to a throttle). This both saves work and prevents false
|
|
* next-buddy nomination below.
|
|
*/
|
|
if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
|
|
return;
|
|
|
|
if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
|
|
set_next_buddy(pse);
|
|
next_buddy_marked = 1;
|
|
}
|
|
|
|
/*
|
|
* We can come here with TIF_NEED_RESCHED already set from new task
|
|
* wake up path.
|
|
*
|
|
* Note: this also catches the edge-case of curr being in a throttled
|
|
* group (e.g. via set_curr_task), since update_curr() (in the
|
|
* enqueue of curr) will have resulted in resched being set. This
|
|
* prevents us from potentially nominating it as a false LAST_BUDDY
|
|
* below.
|
|
*/
|
|
if (test_tsk_need_resched(curr))
|
|
return;
|
|
|
|
/* Idle tasks are by definition preempted by non-idle tasks. */
|
|
if (unlikely(task_has_idle_policy(curr)) &&
|
|
likely(!task_has_idle_policy(p)))
|
|
goto preempt;
|
|
|
|
/*
|
|
* Batch and idle tasks do not preempt non-idle tasks (their preemption
|
|
* is driven by the tick):
|
|
*/
|
|
if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
|
|
return;
|
|
|
|
find_matching_se(&se, &pse);
|
|
update_curr(cfs_rq_of(se));
|
|
BUG_ON(!pse);
|
|
if (wakeup_preempt_entity(se, pse) == 1) {
|
|
/*
|
|
* Bias pick_next to pick the sched entity that is
|
|
* triggering this preemption.
|
|
*/
|
|
if (!next_buddy_marked)
|
|
set_next_buddy(pse);
|
|
goto preempt;
|
|
}
|
|
|
|
return;
|
|
|
|
preempt:
|
|
resched_curr(rq);
|
|
/*
|
|
* Only set the backward buddy when the current task is still
|
|
* on the rq. This can happen when a wakeup gets interleaved
|
|
* with schedule on the ->pre_schedule() or idle_balance()
|
|
* point, either of which can * drop the rq lock.
|
|
*
|
|
* Also, during early boot the idle thread is in the fair class,
|
|
* for obvious reasons its a bad idea to schedule back to it.
|
|
*/
|
|
if (unlikely(!se->on_rq || curr == rq->idle))
|
|
return;
|
|
|
|
if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
|
|
set_last_buddy(se);
|
|
}
|
|
|
|
static struct task_struct *
|
|
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
|
|
{
|
|
struct cfs_rq *cfs_rq = &rq->cfs;
|
|
struct sched_entity *se;
|
|
struct task_struct *p;
|
|
int new_tasks;
|
|
|
|
again:
|
|
if (!cfs_rq->nr_running)
|
|
goto idle;
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
if (prev->sched_class != &fair_sched_class)
|
|
goto simple;
|
|
|
|
/*
|
|
* Because of the set_next_buddy() in dequeue_task_fair() it is rather
|
|
* likely that a next task is from the same cgroup as the current.
|
|
*
|
|
* Therefore attempt to avoid putting and setting the entire cgroup
|
|
* hierarchy, only change the part that actually changes.
|
|
*/
|
|
|
|
do {
|
|
struct sched_entity *curr = cfs_rq->curr;
|
|
|
|
/*
|
|
* Since we got here without doing put_prev_entity() we also
|
|
* have to consider cfs_rq->curr. If it is still a runnable
|
|
* entity, update_curr() will update its vruntime, otherwise
|
|
* forget we've ever seen it.
|
|
*/
|
|
if (curr) {
|
|
if (curr->on_rq)
|
|
update_curr(cfs_rq);
|
|
else
|
|
curr = NULL;
|
|
|
|
/*
|
|
* This call to check_cfs_rq_runtime() will do the
|
|
* throttle and dequeue its entity in the parent(s).
|
|
* Therefore the nr_running test will indeed
|
|
* be correct.
|
|
*/
|
|
if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
|
|
cfs_rq = &rq->cfs;
|
|
|
|
if (!cfs_rq->nr_running)
|
|
goto idle;
|
|
|
|
goto simple;
|
|
}
|
|
}
|
|
|
|
se = pick_next_entity(cfs_rq, curr);
|
|
cfs_rq = group_cfs_rq(se);
|
|
} while (cfs_rq);
|
|
|
|
p = task_of(se);
|
|
|
|
/*
|
|
* Since we haven't yet done put_prev_entity and if the selected task
|
|
* is a different task than we started out with, try and touch the
|
|
* least amount of cfs_rqs.
|
|
*/
|
|
if (prev != p) {
|
|
struct sched_entity *pse = &prev->se;
|
|
|
|
while (!(cfs_rq = is_same_group(se, pse))) {
|
|
int se_depth = se->depth;
|
|
int pse_depth = pse->depth;
|
|
|
|
if (se_depth <= pse_depth) {
|
|
put_prev_entity(cfs_rq_of(pse), pse);
|
|
pse = parent_entity(pse);
|
|
}
|
|
if (se_depth >= pse_depth) {
|
|
set_next_entity(cfs_rq_of(se), se);
|
|
se = parent_entity(se);
|
|
}
|
|
}
|
|
|
|
put_prev_entity(cfs_rq, pse);
|
|
set_next_entity(cfs_rq, se);
|
|
}
|
|
|
|
goto done;
|
|
simple:
|
|
#endif
|
|
|
|
put_prev_task(rq, prev);
|
|
|
|
do {
|
|
se = pick_next_entity(cfs_rq, NULL);
|
|
set_next_entity(cfs_rq, se);
|
|
cfs_rq = group_cfs_rq(se);
|
|
} while (cfs_rq);
|
|
|
|
p = task_of(se);
|
|
|
|
done: __maybe_unused;
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* Move the next running task to the front of
|
|
* the list, so our cfs_tasks list becomes MRU
|
|
* one.
|
|
*/
|
|
list_move(&p->se.group_node, &rq->cfs_tasks);
|
|
#endif
|
|
|
|
if (hrtick_enabled(rq))
|
|
hrtick_start_fair(rq, p);
|
|
|
|
update_misfit_status(p, rq);
|
|
|
|
return p;
|
|
|
|
idle:
|
|
update_misfit_status(NULL, rq);
|
|
new_tasks = idle_balance(rq, rf);
|
|
|
|
/*
|
|
* Because idle_balance() releases (and re-acquires) rq->lock, it is
|
|
* possible for any higher priority task to appear. In that case we
|
|
* must re-start the pick_next_entity() loop.
|
|
*/
|
|
if (new_tasks < 0)
|
|
return RETRY_TASK;
|
|
|
|
if (new_tasks > 0)
|
|
goto again;
|
|
|
|
/*
|
|
* rq is about to be idle, check if we need to update the
|
|
* lost_idle_time of clock_pelt
|
|
*/
|
|
update_idle_rq_clock_pelt(rq);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* Account for a descheduled task:
|
|
*/
|
|
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
|
|
{
|
|
struct sched_entity *se = &prev->se;
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
put_prev_entity(cfs_rq, se);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* sched_yield() is very simple
|
|
*
|
|
* The magic of dealing with the ->skip buddy is in pick_next_entity.
|
|
*/
|
|
static void yield_task_fair(struct rq *rq)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
|
struct sched_entity *se = &curr->se;
|
|
|
|
/*
|
|
* Are we the only task in the tree?
|
|
*/
|
|
if (unlikely(rq->nr_running == 1))
|
|
return;
|
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
if (curr->policy != SCHED_BATCH) {
|
|
update_rq_clock(rq);
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
/*
|
|
* Tell update_rq_clock() that we've just updated,
|
|
* so we don't do microscopic update in schedule()
|
|
* and double the fastpath cost.
|
|
*/
|
|
rq_clock_skip_update(rq);
|
|
}
|
|
|
|
set_skip_buddy(se);
|
|
}
|
|
|
|
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
|
|
/* throttled hierarchies are not runnable */
|
|
if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
|
|
return false;
|
|
|
|
/* Tell the scheduler that we'd really like pse to run next. */
|
|
set_next_buddy(se);
|
|
|
|
yield_task_fair(rq);
|
|
|
|
return true;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/**************************************************
|
|
* Fair scheduling class load-balancing methods.
|
|
*
|
|
* BASICS
|
|
*
|
|
* The purpose of load-balancing is to achieve the same basic fairness the
|
|
* per-CPU scheduler provides, namely provide a proportional amount of compute
|
|
* time to each task. This is expressed in the following equation:
|
|
*
|
|
* W_i,n/P_i == W_j,n/P_j for all i,j (1)
|
|
*
|
|
* Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
|
|
* W_i,0 is defined as:
|
|
*
|
|
* W_i,0 = \Sum_j w_i,j (2)
|
|
*
|
|
* Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
|
|
* is derived from the nice value as per sched_prio_to_weight[].
|
|
*
|
|
* The weight average is an exponential decay average of the instantaneous
|
|
* weight:
|
|
*
|
|
* W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
|
|
*
|
|
* C_i is the compute capacity of CPU i, typically it is the
|
|
* fraction of 'recent' time available for SCHED_OTHER task execution. But it
|
|
* can also include other factors [XXX].
|
|
*
|
|
* To achieve this balance we define a measure of imbalance which follows
|
|
* directly from (1):
|
|
*
|
|
* imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
|
|
*
|
|
* We them move tasks around to minimize the imbalance. In the continuous
|
|
* function space it is obvious this converges, in the discrete case we get
|
|
* a few fun cases generally called infeasible weight scenarios.
|
|
*
|
|
* [XXX expand on:
|
|
* - infeasible weights;
|
|
* - local vs global optima in the discrete case. ]
|
|
*
|
|
*
|
|
* SCHED DOMAINS
|
|
*
|
|
* In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
|
|
* for all i,j solution, we create a tree of CPUs that follows the hardware
|
|
* topology where each level pairs two lower groups (or better). This results
|
|
* in O(log n) layers. Furthermore we reduce the number of CPUs going up the
|
|
* tree to only the first of the previous level and we decrease the frequency
|
|
* of load-balance at each level inv. proportional to the number of CPUs in
|
|
* the groups.
|
|
*
|
|
* This yields:
|
|
*
|
|
* log_2 n 1 n
|
|
* \Sum { --- * --- * 2^i } = O(n) (5)
|
|
* i = 0 2^i 2^i
|
|
* `- size of each group
|
|
* | | `- number of CPUs doing load-balance
|
|
* | `- freq
|
|
* `- sum over all levels
|
|
*
|
|
* Coupled with a limit on how many tasks we can migrate every balance pass,
|
|
* this makes (5) the runtime complexity of the balancer.
|
|
*
|
|
* An important property here is that each CPU is still (indirectly) connected
|
|
* to every other CPU in at most O(log n) steps:
|
|
*
|
|
* The adjacency matrix of the resulting graph is given by:
|
|
*
|
|
* log_2 n
|
|
* A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
|
|
* k = 0
|
|
*
|
|
* And you'll find that:
|
|
*
|
|
* A^(log_2 n)_i,j != 0 for all i,j (7)
|
|
*
|
|
* Showing there's indeed a path between every CPU in at most O(log n) steps.
|
|
* The task movement gives a factor of O(m), giving a convergence complexity
|
|
* of:
|
|
*
|
|
* O(nm log n), n := nr_cpus, m := nr_tasks (8)
|
|
*
|
|
*
|
|
* WORK CONSERVING
|
|
*
|
|
* In order to avoid CPUs going idle while there's still work to do, new idle
|
|
* balancing is more aggressive and has the newly idle CPU iterate up the domain
|
|
* tree itself instead of relying on other CPUs to bring it work.
|
|
*
|
|
* This adds some complexity to both (5) and (8) but it reduces the total idle
|
|
* time.
|
|
*
|
|
* [XXX more?]
|
|
*
|
|
*
|
|
* CGROUPS
|
|
*
|
|
* Cgroups make a horror show out of (2), instead of a simple sum we get:
|
|
*
|
|
* s_k,i
|
|
* W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
|
|
* S_k
|
|
*
|
|
* Where
|
|
*
|
|
* s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
|
|
*
|
|
* w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
|
|
*
|
|
* The big problem is S_k, its a global sum needed to compute a local (W_i)
|
|
* property.
|
|
*
|
|
* [XXX write more on how we solve this.. _after_ merging pjt's patches that
|
|
* rewrite all of this once again.]
|
|
*/
|
|
|
|
static unsigned long __read_mostly max_load_balance_interval = HZ/10;
|
|
|
|
enum fbq_type { regular, remote, all };
|
|
|
|
enum group_type {
|
|
group_other = 0,
|
|
group_misfit_task,
|
|
group_imbalanced,
|
|
group_overloaded,
|
|
};
|
|
|
|
#define LBF_ALL_PINNED 0x01
|
|
#define LBF_NEED_BREAK 0x02
|
|
#define LBF_DST_PINNED 0x04
|
|
#define LBF_SOME_PINNED 0x08
|
|
#define LBF_NOHZ_STATS 0x10
|
|
#define LBF_NOHZ_AGAIN 0x20
|
|
|
|
struct lb_env {
|
|
struct sched_domain *sd;
|
|
|
|
struct rq *src_rq;
|
|
int src_cpu;
|
|
|
|
int dst_cpu;
|
|
struct rq *dst_rq;
|
|
|
|
struct cpumask *dst_grpmask;
|
|
int new_dst_cpu;
|
|
enum cpu_idle_type idle;
|
|
long imbalance;
|
|
/* The set of CPUs under consideration for load-balancing */
|
|
struct cpumask *cpus;
|
|
|
|
unsigned int flags;
|
|
|
|
unsigned int loop;
|
|
unsigned int loop_break;
|
|
unsigned int loop_max;
|
|
|
|
enum fbq_type fbq_type;
|
|
enum group_type src_grp_type;
|
|
struct list_head tasks;
|
|
};
|
|
|
|
/*
|
|
* Is this task likely cache-hot:
|
|
*/
|
|
static int task_hot(struct task_struct *p, struct lb_env *env)
|
|
{
|
|
s64 delta;
|
|
|
|
lockdep_assert_held(&env->src_rq->lock);
|
|
|
|
if (p->sched_class != &fair_sched_class)
|
|
return 0;
|
|
|
|
if (unlikely(task_has_idle_policy(p)))
|
|
return 0;
|
|
|
|
/*
|
|
* Buddy candidates are cache hot:
|
|
*/
|
|
if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
|
|
(&p->se == cfs_rq_of(&p->se)->next ||
|
|
&p->se == cfs_rq_of(&p->se)->last))
|
|
return 1;
|
|
|
|
if (sysctl_sched_migration_cost == -1)
|
|
return 1;
|
|
if (sysctl_sched_migration_cost == 0)
|
|
return 0;
|
|
|
|
delta = rq_clock_task(env->src_rq) - p->se.exec_start;
|
|
|
|
return delta < (s64)sysctl_sched_migration_cost;
|
|
}
|
|
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
/*
|
|
* Returns 1, if task migration degrades locality
|
|
* Returns 0, if task migration improves locality i.e migration preferred.
|
|
* Returns -1, if task migration is not affected by locality.
|
|
*/
|
|
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
|
|
{
|
|
struct numa_group *numa_group = rcu_dereference(p->numa_group);
|
|
unsigned long src_weight, dst_weight;
|
|
int src_nid, dst_nid, dist;
|
|
|
|
if (!static_branch_likely(&sched_numa_balancing))
|
|
return -1;
|
|
|
|
if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
|
|
return -1;
|
|
|
|
src_nid = cpu_to_node(env->src_cpu);
|
|
dst_nid = cpu_to_node(env->dst_cpu);
|
|
|
|
if (src_nid == dst_nid)
|
|
return -1;
|
|
|
|
/* Migrating away from the preferred node is always bad. */
|
|
if (src_nid == p->numa_preferred_nid) {
|
|
if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
|
|
return 1;
|
|
else
|
|
return -1;
|
|
}
|
|
|
|
/* Encourage migration to the preferred node. */
|
|
if (dst_nid == p->numa_preferred_nid)
|
|
return 0;
|
|
|
|
/* Leaving a core idle is often worse than degrading locality. */
|
|
if (env->idle == CPU_IDLE)
|
|
return -1;
|
|
|
|
dist = node_distance(src_nid, dst_nid);
|
|
if (numa_group) {
|
|
src_weight = group_weight(p, src_nid, dist);
|
|
dst_weight = group_weight(p, dst_nid, dist);
|
|
} else {
|
|
src_weight = task_weight(p, src_nid, dist);
|
|
dst_weight = task_weight(p, dst_nid, dist);
|
|
}
|
|
|
|
return dst_weight < src_weight;
|
|
}
|
|
|
|
#else
|
|
static inline int migrate_degrades_locality(struct task_struct *p,
|
|
struct lb_env *env)
|
|
{
|
|
return -1;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
|
|
*/
|
|
static
|
|
int can_migrate_task(struct task_struct *p, struct lb_env *env)
|
|
{
|
|
int tsk_cache_hot;
|
|
|
|
lockdep_assert_held(&env->src_rq->lock);
|
|
|
|
/*
|
|
* We do not migrate tasks that are:
|
|
* 1) throttled_lb_pair, or
|
|
* 2) cannot be migrated to this CPU due to cpus_allowed, or
|
|
* 3) running (obviously), or
|
|
* 4) are cache-hot on their current CPU.
|
|
*/
|
|
if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
|
|
return 0;
|
|
|
|
if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
|
|
int cpu;
|
|
|
|
schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
|
|
|
|
env->flags |= LBF_SOME_PINNED;
|
|
|
|
/*
|
|
* Remember if this task can be migrated to any other CPU in
|
|
* our sched_group. We may want to revisit it if we couldn't
|
|
* meet load balance goals by pulling other tasks on src_cpu.
|
|
*
|
|
* Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
|
|
* already computed one in current iteration.
|
|
*/
|
|
if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
|
|
return 0;
|
|
|
|
/* Prevent to re-select dst_cpu via env's CPUs: */
|
|
for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
|
|
if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
|
|
env->flags |= LBF_DST_PINNED;
|
|
env->new_dst_cpu = cpu;
|
|
break;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Record that we found atleast one task that could run on dst_cpu */
|
|
env->flags &= ~LBF_ALL_PINNED;
|
|
|
|
if (task_running(env->src_rq, p)) {
|
|
schedstat_inc(p->se.statistics.nr_failed_migrations_running);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Aggressive migration if:
|
|
* 1) destination numa is preferred
|
|
* 2) task is cache cold, or
|
|
* 3) too many balance attempts have failed.
|
|
*/
|
|
tsk_cache_hot = migrate_degrades_locality(p, env);
|
|
if (tsk_cache_hot == -1)
|
|
tsk_cache_hot = task_hot(p, env);
|
|
|
|
if (tsk_cache_hot <= 0 ||
|
|
env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
|
|
if (tsk_cache_hot == 1) {
|
|
schedstat_inc(env->sd->lb_hot_gained[env->idle]);
|
|
schedstat_inc(p->se.statistics.nr_forced_migrations);
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* detach_task() -- detach the task for the migration specified in env
|
|
*/
|
|
static void detach_task(struct task_struct *p, struct lb_env *env)
|
|
{
|
|
lockdep_assert_held(&env->src_rq->lock);
|
|
|
|
p->on_rq = TASK_ON_RQ_MIGRATING;
|
|
deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
|
|
set_task_cpu(p, env->dst_cpu);
|
|
}
|
|
|
|
/*
|
|
* detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
|
|
* part of active balancing operations within "domain".
|
|
*
|
|
* Returns a task if successful and NULL otherwise.
|
|
*/
|
|
static struct task_struct *detach_one_task(struct lb_env *env)
|
|
{
|
|
struct task_struct *p;
|
|
|
|
lockdep_assert_held(&env->src_rq->lock);
|
|
|
|
list_for_each_entry_reverse(p,
|
|
&env->src_rq->cfs_tasks, se.group_node) {
|
|
if (!can_migrate_task(p, env))
|
|
continue;
|
|
|
|
detach_task(p, env);
|
|
|
|
/*
|
|
* Right now, this is only the second place where
|
|
* lb_gained[env->idle] is updated (other is detach_tasks)
|
|
* so we can safely collect stats here rather than
|
|
* inside detach_tasks().
|
|
*/
|
|
schedstat_inc(env->sd->lb_gained[env->idle]);
|
|
return p;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
static const unsigned int sched_nr_migrate_break = 32;
|
|
|
|
/*
|
|
* detach_tasks() -- tries to detach up to imbalance weighted load from
|
|
* busiest_rq, as part of a balancing operation within domain "sd".
|
|
*
|
|
* Returns number of detached tasks if successful and 0 otherwise.
|
|
*/
|
|
static int detach_tasks(struct lb_env *env)
|
|
{
|
|
struct list_head *tasks = &env->src_rq->cfs_tasks;
|
|
struct task_struct *p;
|
|
unsigned long load;
|
|
int detached = 0;
|
|
|
|
lockdep_assert_held(&env->src_rq->lock);
|
|
|
|
if (env->imbalance <= 0)
|
|
return 0;
|
|
|
|
while (!list_empty(tasks)) {
|
|
/*
|
|
* We don't want to steal all, otherwise we may be treated likewise,
|
|
* which could at worst lead to a livelock crash.
|
|
*/
|
|
if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
|
|
break;
|
|
|
|
p = list_last_entry(tasks, struct task_struct, se.group_node);
|
|
|
|
env->loop++;
|
|
/* We've more or less seen every task there is, call it quits */
|
|
if (env->loop > env->loop_max)
|
|
break;
|
|
|
|
/* take a breather every nr_migrate tasks */
|
|
if (env->loop > env->loop_break) {
|
|
env->loop_break += sched_nr_migrate_break;
|
|
env->flags |= LBF_NEED_BREAK;
|
|
break;
|
|
}
|
|
|
|
if (!can_migrate_task(p, env))
|
|
goto next;
|
|
|
|
load = task_h_load(p);
|
|
|
|
if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
|
|
goto next;
|
|
|
|
if ((load / 2) > env->imbalance)
|
|
goto next;
|
|
|
|
detach_task(p, env);
|
|
list_add(&p->se.group_node, &env->tasks);
|
|
|
|
detached++;
|
|
env->imbalance -= load;
|
|
|
|
#ifdef CONFIG_PREEMPT
|
|
/*
|
|
* NEWIDLE balancing is a source of latency, so preemptible
|
|
* kernels will stop after the first task is detached to minimize
|
|
* the critical section.
|
|
*/
|
|
if (env->idle == CPU_NEWLY_IDLE)
|
|
break;
|
|
#endif
|
|
|
|
/*
|
|
* We only want to steal up to the prescribed amount of
|
|
* weighted load.
|
|
*/
|
|
if (env->imbalance <= 0)
|
|
break;
|
|
|
|
continue;
|
|
next:
|
|
list_move(&p->se.group_node, tasks);
|
|
}
|
|
|
|
/*
|
|
* Right now, this is one of only two places we collect this stat
|
|
* so we can safely collect detach_one_task() stats here rather
|
|
* than inside detach_one_task().
|
|
*/
|
|
schedstat_add(env->sd->lb_gained[env->idle], detached);
|
|
|
|
return detached;
|
|
}
|
|
|
|
/*
|
|
* attach_task() -- attach the task detached by detach_task() to its new rq.
|
|
*/
|
|
static void attach_task(struct rq *rq, struct task_struct *p)
|
|
{
|
|
lockdep_assert_held(&rq->lock);
|
|
|
|
BUG_ON(task_rq(p) != rq);
|
|
activate_task(rq, p, ENQUEUE_NOCLOCK);
|
|
p->on_rq = TASK_ON_RQ_QUEUED;
|
|
check_preempt_curr(rq, p, 0);
|
|
}
|
|
|
|
/*
|
|
* attach_one_task() -- attaches the task returned from detach_one_task() to
|
|
* its new rq.
|
|
*/
|
|
static void attach_one_task(struct rq *rq, struct task_struct *p)
|
|
{
|
|
struct rq_flags rf;
|
|
|
|
rq_lock(rq, &rf);
|
|
update_rq_clock(rq);
|
|
attach_task(rq, p);
|
|
rq_unlock(rq, &rf);
|
|
}
|
|
|
|
/*
|
|
* attach_tasks() -- attaches all tasks detached by detach_tasks() to their
|
|
* new rq.
|
|
*/
|
|
static void attach_tasks(struct lb_env *env)
|
|
{
|
|
struct list_head *tasks = &env->tasks;
|
|
struct task_struct *p;
|
|
struct rq_flags rf;
|
|
|
|
rq_lock(env->dst_rq, &rf);
|
|
update_rq_clock(env->dst_rq);
|
|
|
|
while (!list_empty(tasks)) {
|
|
p = list_first_entry(tasks, struct task_struct, se.group_node);
|
|
list_del_init(&p->se.group_node);
|
|
|
|
attach_task(env->dst_rq, p);
|
|
}
|
|
|
|
rq_unlock(env->dst_rq, &rf);
|
|
}
|
|
|
|
static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (cfs_rq->avg.load_avg)
|
|
return true;
|
|
|
|
if (cfs_rq->avg.util_avg)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static inline bool others_have_blocked(struct rq *rq)
|
|
{
|
|
if (READ_ONCE(rq->avg_rt.util_avg))
|
|
return true;
|
|
|
|
if (READ_ONCE(rq->avg_dl.util_avg))
|
|
return true;
|
|
|
|
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
|
|
if (READ_ONCE(rq->avg_irq.util_avg))
|
|
return true;
|
|
#endif
|
|
|
|
return false;
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
|
|
static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
|
|
{
|
|
if (cfs_rq->load.weight)
|
|
return false;
|
|
|
|
if (cfs_rq->avg.load_sum)
|
|
return false;
|
|
|
|
if (cfs_rq->avg.util_sum)
|
|
return false;
|
|
|
|
if (cfs_rq->avg.runnable_load_sum)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
static void update_blocked_averages(int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
struct cfs_rq *cfs_rq, *pos;
|
|
const struct sched_class *curr_class;
|
|
struct rq_flags rf;
|
|
bool done = true;
|
|
|
|
rq_lock_irqsave(rq, &rf);
|
|
update_rq_clock(rq);
|
|
|
|
/*
|
|
* Iterates the task_group tree in a bottom up fashion, see
|
|
* list_add_leaf_cfs_rq() for details.
|
|
*/
|
|
for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
|
|
struct sched_entity *se;
|
|
|
|
if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq))
|
|
update_tg_load_avg(cfs_rq, 0);
|
|
|
|
/* Propagate pending load changes to the parent, if any: */
|
|
se = cfs_rq->tg->se[cpu];
|
|
if (se && !skip_blocked_update(se))
|
|
update_load_avg(cfs_rq_of(se), se, 0);
|
|
|
|
/*
|
|
* There can be a lot of idle CPU cgroups. Don't let fully
|
|
* decayed cfs_rqs linger on the list.
|
|
*/
|
|
if (cfs_rq_is_decayed(cfs_rq))
|
|
list_del_leaf_cfs_rq(cfs_rq);
|
|
|
|
/* Don't need periodic decay once load/util_avg are null */
|
|
if (cfs_rq_has_blocked(cfs_rq))
|
|
done = false;
|
|
}
|
|
|
|
curr_class = rq->curr->sched_class;
|
|
update_rt_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &rt_sched_class);
|
|
update_dl_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &dl_sched_class);
|
|
update_irq_load_avg(rq, 0);
|
|
/* Don't need periodic decay once load/util_avg are null */
|
|
if (others_have_blocked(rq))
|
|
done = false;
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
rq->last_blocked_load_update_tick = jiffies;
|
|
if (done)
|
|
rq->has_blocked_load = 0;
|
|
#endif
|
|
rq_unlock_irqrestore(rq, &rf);
|
|
}
|
|
|
|
/*
|
|
* Compute the hierarchical load factor for cfs_rq and all its ascendants.
|
|
* This needs to be done in a top-down fashion because the load of a child
|
|
* group is a fraction of its parents load.
|
|
*/
|
|
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct rq *rq = rq_of(cfs_rq);
|
|
struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
|
|
unsigned long now = jiffies;
|
|
unsigned long load;
|
|
|
|
if (cfs_rq->last_h_load_update == now)
|
|
return;
|
|
|
|
cfs_rq->h_load_next = NULL;
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
cfs_rq->h_load_next = se;
|
|
if (cfs_rq->last_h_load_update == now)
|
|
break;
|
|
}
|
|
|
|
if (!se) {
|
|
cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
|
|
cfs_rq->last_h_load_update = now;
|
|
}
|
|
|
|
while ((se = cfs_rq->h_load_next) != NULL) {
|
|
load = cfs_rq->h_load;
|
|
load = div64_ul(load * se->avg.load_avg,
|
|
cfs_rq_load_avg(cfs_rq) + 1);
|
|
cfs_rq = group_cfs_rq(se);
|
|
cfs_rq->h_load = load;
|
|
cfs_rq->last_h_load_update = now;
|
|
}
|
|
}
|
|
|
|
static unsigned long task_h_load(struct task_struct *p)
|
|
{
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(p);
|
|
|
|
update_cfs_rq_h_load(cfs_rq);
|
|
return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
|
|
cfs_rq_load_avg(cfs_rq) + 1);
|
|
}
|
|
#else
|
|
static inline void update_blocked_averages(int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
struct cfs_rq *cfs_rq = &rq->cfs;
|
|
const struct sched_class *curr_class;
|
|
struct rq_flags rf;
|
|
|
|
rq_lock_irqsave(rq, &rf);
|
|
update_rq_clock(rq);
|
|
update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
|
|
|
|
curr_class = rq->curr->sched_class;
|
|
update_rt_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &rt_sched_class);
|
|
update_dl_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &dl_sched_class);
|
|
update_irq_load_avg(rq, 0);
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
rq->last_blocked_load_update_tick = jiffies;
|
|
if (!cfs_rq_has_blocked(cfs_rq) && !others_have_blocked(rq))
|
|
rq->has_blocked_load = 0;
|
|
#endif
|
|
rq_unlock_irqrestore(rq, &rf);
|
|
}
|
|
|
|
static unsigned long task_h_load(struct task_struct *p)
|
|
{
|
|
return p->se.avg.load_avg;
|
|
}
|
|
#endif
|
|
|
|
/********** Helpers for find_busiest_group ************************/
|
|
|
|
/*
|
|
* sg_lb_stats - stats of a sched_group required for load_balancing
|
|
*/
|
|
struct sg_lb_stats {
|
|
unsigned long avg_load; /*Avg load across the CPUs of the group */
|
|
unsigned long group_load; /* Total load over the CPUs of the group */
|
|
unsigned long sum_weighted_load; /* Weighted load of group's tasks */
|
|
unsigned long load_per_task;
|
|
unsigned long group_capacity;
|
|
unsigned long group_util; /* Total utilization of the group */
|
|
unsigned int sum_nr_running; /* Nr tasks running in the group */
|
|
unsigned int idle_cpus;
|
|
unsigned int group_weight;
|
|
enum group_type group_type;
|
|
int group_no_capacity;
|
|
unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
unsigned int nr_numa_running;
|
|
unsigned int nr_preferred_running;
|
|
#endif
|
|
};
|
|
|
|
/*
|
|
* sd_lb_stats - Structure to store the statistics of a sched_domain
|
|
* during load balancing.
|
|
*/
|
|
struct sd_lb_stats {
|
|
struct sched_group *busiest; /* Busiest group in this sd */
|
|
struct sched_group *local; /* Local group in this sd */
|
|
unsigned long total_running;
|
|
unsigned long total_load; /* Total load of all groups in sd */
|
|
unsigned long total_capacity; /* Total capacity of all groups in sd */
|
|
unsigned long avg_load; /* Average load across all groups in sd */
|
|
|
|
struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
|
|
struct sg_lb_stats local_stat; /* Statistics of the local group */
|
|
};
|
|
|
|
static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
|
|
{
|
|
/*
|
|
* Skimp on the clearing to avoid duplicate work. We can avoid clearing
|
|
* local_stat because update_sg_lb_stats() does a full clear/assignment.
|
|
* We must however clear busiest_stat::avg_load because
|
|
* update_sd_pick_busiest() reads this before assignment.
|
|
*/
|
|
*sds = (struct sd_lb_stats){
|
|
.busiest = NULL,
|
|
.local = NULL,
|
|
.total_running = 0UL,
|
|
.total_load = 0UL,
|
|
.total_capacity = 0UL,
|
|
.busiest_stat = {
|
|
.avg_load = 0UL,
|
|
.sum_nr_running = 0,
|
|
.group_type = group_other,
|
|
},
|
|
};
|
|
}
|
|
|
|
/**
|
|
* get_sd_load_idx - Obtain the load index for a given sched domain.
|
|
* @sd: The sched_domain whose load_idx is to be obtained.
|
|
* @idle: The idle status of the CPU for whose sd load_idx is obtained.
|
|
*
|
|
* Return: The load index.
|
|
*/
|
|
static inline int get_sd_load_idx(struct sched_domain *sd,
|
|
enum cpu_idle_type idle)
|
|
{
|
|
int load_idx;
|
|
|
|
switch (idle) {
|
|
case CPU_NOT_IDLE:
|
|
load_idx = sd->busy_idx;
|
|
break;
|
|
|
|
case CPU_NEWLY_IDLE:
|
|
load_idx = sd->newidle_idx;
|
|
break;
|
|
default:
|
|
load_idx = sd->idle_idx;
|
|
break;
|
|
}
|
|
|
|
return load_idx;
|
|
}
|
|
|
|
static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long max = arch_scale_cpu_capacity(sd, cpu);
|
|
unsigned long used, free;
|
|
unsigned long irq;
|
|
|
|
irq = cpu_util_irq(rq);
|
|
|
|
if (unlikely(irq >= max))
|
|
return 1;
|
|
|
|
used = READ_ONCE(rq->avg_rt.util_avg);
|
|
used += READ_ONCE(rq->avg_dl.util_avg);
|
|
|
|
if (unlikely(used >= max))
|
|
return 1;
|
|
|
|
free = max - used;
|
|
|
|
return scale_irq_capacity(free, irq, max);
|
|
}
|
|
|
|
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
|
|
{
|
|
unsigned long capacity = scale_rt_capacity(sd, cpu);
|
|
struct sched_group *sdg = sd->groups;
|
|
|
|
cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(sd, cpu);
|
|
|
|
if (!capacity)
|
|
capacity = 1;
|
|
|
|
cpu_rq(cpu)->cpu_capacity = capacity;
|
|
sdg->sgc->capacity = capacity;
|
|
sdg->sgc->min_capacity = capacity;
|
|
sdg->sgc->max_capacity = capacity;
|
|
}
|
|
|
|
void update_group_capacity(struct sched_domain *sd, int cpu)
|
|
{
|
|
struct sched_domain *child = sd->child;
|
|
struct sched_group *group, *sdg = sd->groups;
|
|
unsigned long capacity, min_capacity, max_capacity;
|
|
unsigned long interval;
|
|
|
|
interval = msecs_to_jiffies(sd->balance_interval);
|
|
interval = clamp(interval, 1UL, max_load_balance_interval);
|
|
sdg->sgc->next_update = jiffies + interval;
|
|
|
|
if (!child) {
|
|
update_cpu_capacity(sd, cpu);
|
|
return;
|
|
}
|
|
|
|
capacity = 0;
|
|
min_capacity = ULONG_MAX;
|
|
max_capacity = 0;
|
|
|
|
if (child->flags & SD_OVERLAP) {
|
|
/*
|
|
* SD_OVERLAP domains cannot assume that child groups
|
|
* span the current group.
|
|
*/
|
|
|
|
for_each_cpu(cpu, sched_group_span(sdg)) {
|
|
struct sched_group_capacity *sgc;
|
|
struct rq *rq = cpu_rq(cpu);
|
|
|
|
/*
|
|
* build_sched_domains() -> init_sched_groups_capacity()
|
|
* gets here before we've attached the domains to the
|
|
* runqueues.
|
|
*
|
|
* Use capacity_of(), which is set irrespective of domains
|
|
* in update_cpu_capacity().
|
|
*
|
|
* This avoids capacity from being 0 and
|
|
* causing divide-by-zero issues on boot.
|
|
*/
|
|
if (unlikely(!rq->sd)) {
|
|
capacity += capacity_of(cpu);
|
|
} else {
|
|
sgc = rq->sd->groups->sgc;
|
|
capacity += sgc->capacity;
|
|
}
|
|
|
|
min_capacity = min(capacity, min_capacity);
|
|
max_capacity = max(capacity, max_capacity);
|
|
}
|
|
} else {
|
|
/*
|
|
* !SD_OVERLAP domains can assume that child groups
|
|
* span the current group.
|
|
*/
|
|
|
|
group = child->groups;
|
|
do {
|
|
struct sched_group_capacity *sgc = group->sgc;
|
|
|
|
capacity += sgc->capacity;
|
|
min_capacity = min(sgc->min_capacity, min_capacity);
|
|
max_capacity = max(sgc->max_capacity, max_capacity);
|
|
group = group->next;
|
|
} while (group != child->groups);
|
|
}
|
|
|
|
sdg->sgc->capacity = capacity;
|
|
sdg->sgc->min_capacity = min_capacity;
|
|
sdg->sgc->max_capacity = max_capacity;
|
|
}
|
|
|
|
/*
|
|
* Check whether the capacity of the rq has been noticeably reduced by side
|
|
* activity. The imbalance_pct is used for the threshold.
|
|
* Return true is the capacity is reduced
|
|
*/
|
|
static inline int
|
|
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
|
|
{
|
|
return ((rq->cpu_capacity * sd->imbalance_pct) <
|
|
(rq->cpu_capacity_orig * 100));
|
|
}
|
|
|
|
/*
|
|
* Check whether a rq has a misfit task and if it looks like we can actually
|
|
* help that task: we can migrate the task to a CPU of higher capacity, or
|
|
* the task's current CPU is heavily pressured.
|
|
*/
|
|
static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
|
|
{
|
|
return rq->misfit_task_load &&
|
|
(rq->cpu_capacity_orig < rq->rd->max_cpu_capacity ||
|
|
check_cpu_capacity(rq, sd));
|
|
}
|
|
|
|
/*
|
|
* Group imbalance indicates (and tries to solve) the problem where balancing
|
|
* groups is inadequate due to ->cpus_allowed constraints.
|
|
*
|
|
* Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
|
|
* cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
|
|
* Something like:
|
|
*
|
|
* { 0 1 2 3 } { 4 5 6 7 }
|
|
* * * * *
|
|
*
|
|
* If we were to balance group-wise we'd place two tasks in the first group and
|
|
* two tasks in the second group. Clearly this is undesired as it will overload
|
|
* cpu 3 and leave one of the CPUs in the second group unused.
|
|
*
|
|
* The current solution to this issue is detecting the skew in the first group
|
|
* by noticing the lower domain failed to reach balance and had difficulty
|
|
* moving tasks due to affinity constraints.
|
|
*
|
|
* When this is so detected; this group becomes a candidate for busiest; see
|
|
* update_sd_pick_busiest(). And calculate_imbalance() and
|
|
* find_busiest_group() avoid some of the usual balance conditions to allow it
|
|
* to create an effective group imbalance.
|
|
*
|
|
* This is a somewhat tricky proposition since the next run might not find the
|
|
* group imbalance and decide the groups need to be balanced again. A most
|
|
* subtle and fragile situation.
|
|
*/
|
|
|
|
static inline int sg_imbalanced(struct sched_group *group)
|
|
{
|
|
return group->sgc->imbalance;
|
|
}
|
|
|
|
/*
|
|
* group_has_capacity returns true if the group has spare capacity that could
|
|
* be used by some tasks.
|
|
* We consider that a group has spare capacity if the * number of task is
|
|
* smaller than the number of CPUs or if the utilization is lower than the
|
|
* available capacity for CFS tasks.
|
|
* For the latter, we use a threshold to stabilize the state, to take into
|
|
* account the variance of the tasks' load and to return true if the available
|
|
* capacity in meaningful for the load balancer.
|
|
* As an example, an available capacity of 1% can appear but it doesn't make
|
|
* any benefit for the load balance.
|
|
*/
|
|
static inline bool
|
|
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
|
|
{
|
|
if (sgs->sum_nr_running < sgs->group_weight)
|
|
return true;
|
|
|
|
if ((sgs->group_capacity * 100) >
|
|
(sgs->group_util * env->sd->imbalance_pct))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* group_is_overloaded returns true if the group has more tasks than it can
|
|
* handle.
|
|
* group_is_overloaded is not equals to !group_has_capacity because a group
|
|
* with the exact right number of tasks, has no more spare capacity but is not
|
|
* overloaded so both group_has_capacity and group_is_overloaded return
|
|
* false.
|
|
*/
|
|
static inline bool
|
|
group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
|
|
{
|
|
if (sgs->sum_nr_running <= sgs->group_weight)
|
|
return false;
|
|
|
|
if ((sgs->group_capacity * 100) <
|
|
(sgs->group_util * env->sd->imbalance_pct))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller
|
|
* per-CPU capacity than sched_group ref.
|
|
*/
|
|
static inline bool
|
|
group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
|
|
{
|
|
return sg->sgc->min_capacity * capacity_margin <
|
|
ref->sgc->min_capacity * 1024;
|
|
}
|
|
|
|
/*
|
|
* group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller
|
|
* per-CPU capacity_orig than sched_group ref.
|
|
*/
|
|
static inline bool
|
|
group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
|
|
{
|
|
return sg->sgc->max_capacity * capacity_margin <
|
|
ref->sgc->max_capacity * 1024;
|
|
}
|
|
|
|
static inline enum
|
|
group_type group_classify(struct sched_group *group,
|
|
struct sg_lb_stats *sgs)
|
|
{
|
|
if (sgs->group_no_capacity)
|
|
return group_overloaded;
|
|
|
|
if (sg_imbalanced(group))
|
|
return group_imbalanced;
|
|
|
|
if (sgs->group_misfit_task_load)
|
|
return group_misfit_task;
|
|
|
|
return group_other;
|
|
}
|
|
|
|
static bool update_nohz_stats(struct rq *rq, bool force)
|
|
{
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
unsigned int cpu = rq->cpu;
|
|
|
|
if (!rq->has_blocked_load)
|
|
return false;
|
|
|
|
if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
|
|
return false;
|
|
|
|
if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
|
|
return true;
|
|
|
|
update_blocked_averages(cpu);
|
|
|
|
return rq->has_blocked_load;
|
|
#else
|
|
return false;
|
|
#endif
|
|
}
|
|
|
|
/**
|
|
* update_sg_lb_stats - Update sched_group's statistics for load balancing.
|
|
* @env: The load balancing environment.
|
|
* @group: sched_group whose statistics are to be updated.
|
|
* @sgs: variable to hold the statistics for this group.
|
|
* @sg_status: Holds flag indicating the status of the sched_group
|
|
*/
|
|
static inline void update_sg_lb_stats(struct lb_env *env,
|
|
struct sched_group *group,
|
|
struct sg_lb_stats *sgs,
|
|
int *sg_status)
|
|
{
|
|
int local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(group));
|
|
int load_idx = get_sd_load_idx(env->sd, env->idle);
|
|
unsigned long load;
|
|
int i, nr_running;
|
|
|
|
memset(sgs, 0, sizeof(*sgs));
|
|
|
|
for_each_cpu_and(i, sched_group_span(group), env->cpus) {
|
|
struct rq *rq = cpu_rq(i);
|
|
|
|
if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
|
|
env->flags |= LBF_NOHZ_AGAIN;
|
|
|
|
/* Bias balancing toward CPUs of our domain: */
|
|
if (local_group)
|
|
load = target_load(i, load_idx);
|
|
else
|
|
load = source_load(i, load_idx);
|
|
|
|
sgs->group_load += load;
|
|
sgs->group_util += cpu_util(i);
|
|
sgs->sum_nr_running += rq->cfs.h_nr_running;
|
|
|
|
nr_running = rq->nr_running;
|
|
if (nr_running > 1)
|
|
*sg_status |= SG_OVERLOAD;
|
|
|
|
if (cpu_overutilized(i))
|
|
*sg_status |= SG_OVERUTILIZED;
|
|
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
sgs->nr_numa_running += rq->nr_numa_running;
|
|
sgs->nr_preferred_running += rq->nr_preferred_running;
|
|
#endif
|
|
sgs->sum_weighted_load += weighted_cpuload(rq);
|
|
/*
|
|
* No need to call idle_cpu() if nr_running is not 0
|
|
*/
|
|
if (!nr_running && idle_cpu(i))
|
|
sgs->idle_cpus++;
|
|
|
|
if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
|
|
sgs->group_misfit_task_load < rq->misfit_task_load) {
|
|
sgs->group_misfit_task_load = rq->misfit_task_load;
|
|
*sg_status |= SG_OVERLOAD;
|
|
}
|
|
}
|
|
|
|
/* Adjust by relative CPU capacity of the group */
|
|
sgs->group_capacity = group->sgc->capacity;
|
|
sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
|
|
|
|
if (sgs->sum_nr_running)
|
|
sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
|
|
|
|
sgs->group_weight = group->group_weight;
|
|
|
|
sgs->group_no_capacity = group_is_overloaded(env, sgs);
|
|
sgs->group_type = group_classify(group, sgs);
|
|
}
|
|
|
|
/**
|
|
* update_sd_pick_busiest - return 1 on busiest group
|
|
* @env: The load balancing environment.
|
|
* @sds: sched_domain statistics
|
|
* @sg: sched_group candidate to be checked for being the busiest
|
|
* @sgs: sched_group statistics
|
|
*
|
|
* Determine if @sg is a busier group than the previously selected
|
|
* busiest group.
|
|
*
|
|
* Return: %true if @sg is a busier group than the previously selected
|
|
* busiest group. %false otherwise.
|
|
*/
|
|
static bool update_sd_pick_busiest(struct lb_env *env,
|
|
struct sd_lb_stats *sds,
|
|
struct sched_group *sg,
|
|
struct sg_lb_stats *sgs)
|
|
{
|
|
struct sg_lb_stats *busiest = &sds->busiest_stat;
|
|
|
|
/*
|
|
* Don't try to pull misfit tasks we can't help.
|
|
* We can use max_capacity here as reduction in capacity on some
|
|
* CPUs in the group should either be possible to resolve
|
|
* internally or be covered by avg_load imbalance (eventually).
|
|
*/
|
|
if (sgs->group_type == group_misfit_task &&
|
|
(!group_smaller_max_cpu_capacity(sg, sds->local) ||
|
|
!group_has_capacity(env, &sds->local_stat)))
|
|
return false;
|
|
|
|
if (sgs->group_type > busiest->group_type)
|
|
return true;
|
|
|
|
if (sgs->group_type < busiest->group_type)
|
|
return false;
|
|
|
|
if (sgs->avg_load <= busiest->avg_load)
|
|
return false;
|
|
|
|
if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
|
|
goto asym_packing;
|
|
|
|
/*
|
|
* Candidate sg has no more than one task per CPU and
|
|
* has higher per-CPU capacity. Migrating tasks to less
|
|
* capable CPUs may harm throughput. Maximize throughput,
|
|
* power/energy consequences are not considered.
|
|
*/
|
|
if (sgs->sum_nr_running <= sgs->group_weight &&
|
|
group_smaller_min_cpu_capacity(sds->local, sg))
|
|
return false;
|
|
|
|
/*
|
|
* If we have more than one misfit sg go with the biggest misfit.
|
|
*/
|
|
if (sgs->group_type == group_misfit_task &&
|
|
sgs->group_misfit_task_load < busiest->group_misfit_task_load)
|
|
return false;
|
|
|
|
asym_packing:
|
|
/* This is the busiest node in its class. */
|
|
if (!(env->sd->flags & SD_ASYM_PACKING))
|
|
return true;
|
|
|
|
/* No ASYM_PACKING if target CPU is already busy */
|
|
if (env->idle == CPU_NOT_IDLE)
|
|
return true;
|
|
/*
|
|
* ASYM_PACKING needs to move all the work to the highest
|
|
* prority CPUs in the group, therefore mark all groups
|
|
* of lower priority than ourself as busy.
|
|
*/
|
|
if (sgs->sum_nr_running &&
|
|
sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
|
|
if (!sds->busiest)
|
|
return true;
|
|
|
|
/* Prefer to move from lowest priority CPU's work */
|
|
if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
|
|
sg->asym_prefer_cpu))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
|
|
{
|
|
if (sgs->sum_nr_running > sgs->nr_numa_running)
|
|
return regular;
|
|
if (sgs->sum_nr_running > sgs->nr_preferred_running)
|
|
return remote;
|
|
return all;
|
|
}
|
|
|
|
static inline enum fbq_type fbq_classify_rq(struct rq *rq)
|
|
{
|
|
if (rq->nr_running > rq->nr_numa_running)
|
|
return regular;
|
|
if (rq->nr_running > rq->nr_preferred_running)
|
|
return remote;
|
|
return all;
|
|
}
|
|
#else
|
|
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
|
|
{
|
|
return all;
|
|
}
|
|
|
|
static inline enum fbq_type fbq_classify_rq(struct rq *rq)
|
|
{
|
|
return regular;
|
|
}
|
|
#endif /* CONFIG_NUMA_BALANCING */
|
|
|
|
/**
|
|
* update_sd_lb_stats - Update sched_domain's statistics for load balancing.
|
|
* @env: The load balancing environment.
|
|
* @sds: variable to hold the statistics for this sched_domain.
|
|
*/
|
|
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
|
|
{
|
|
struct sched_domain *child = env->sd->child;
|
|
struct sched_group *sg = env->sd->groups;
|
|
struct sg_lb_stats *local = &sds->local_stat;
|
|
struct sg_lb_stats tmp_sgs;
|
|
bool prefer_sibling = child && child->flags & SD_PREFER_SIBLING;
|
|
int sg_status = 0;
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
|
|
env->flags |= LBF_NOHZ_STATS;
|
|
#endif
|
|
|
|
do {
|
|
struct sg_lb_stats *sgs = &tmp_sgs;
|
|
int local_group;
|
|
|
|
local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
|
|
if (local_group) {
|
|
sds->local = sg;
|
|
sgs = local;
|
|
|
|
if (env->idle != CPU_NEWLY_IDLE ||
|
|
time_after_eq(jiffies, sg->sgc->next_update))
|
|
update_group_capacity(env->sd, env->dst_cpu);
|
|
}
|
|
|
|
update_sg_lb_stats(env, sg, sgs, &sg_status);
|
|
|
|
if (local_group)
|
|
goto next_group;
|
|
|
|
/*
|
|
* In case the child domain prefers tasks go to siblings
|
|
* first, lower the sg capacity so that we'll try
|
|
* and move all the excess tasks away. We lower the capacity
|
|
* of a group only if the local group has the capacity to fit
|
|
* these excess tasks. The extra check prevents the case where
|
|
* you always pull from the heaviest group when it is already
|
|
* under-utilized (possible with a large weight task outweighs
|
|
* the tasks on the system).
|
|
*/
|
|
if (prefer_sibling && sds->local &&
|
|
group_has_capacity(env, local) &&
|
|
(sgs->sum_nr_running > local->sum_nr_running + 1)) {
|
|
sgs->group_no_capacity = 1;
|
|
sgs->group_type = group_classify(sg, sgs);
|
|
}
|
|
|
|
if (update_sd_pick_busiest(env, sds, sg, sgs)) {
|
|
sds->busiest = sg;
|
|
sds->busiest_stat = *sgs;
|
|
}
|
|
|
|
next_group:
|
|
/* Now, start updating sd_lb_stats */
|
|
sds->total_running += sgs->sum_nr_running;
|
|
sds->total_load += sgs->group_load;
|
|
sds->total_capacity += sgs->group_capacity;
|
|
|
|
sg = sg->next;
|
|
} while (sg != env->sd->groups);
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
if ((env->flags & LBF_NOHZ_AGAIN) &&
|
|
cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) {
|
|
|
|
WRITE_ONCE(nohz.next_blocked,
|
|
jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD));
|
|
}
|
|
#endif
|
|
|
|
if (env->sd->flags & SD_NUMA)
|
|
env->fbq_type = fbq_classify_group(&sds->busiest_stat);
|
|
|
|
if (!env->sd->parent) {
|
|
struct root_domain *rd = env->dst_rq->rd;
|
|
|
|
/* update overload indicator if we are at root domain */
|
|
WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD);
|
|
|
|
/* Update over-utilization (tipping point, U >= 0) indicator */
|
|
WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
|
|
} else if (sg_status & SG_OVERUTILIZED) {
|
|
WRITE_ONCE(env->dst_rq->rd->overutilized, SG_OVERUTILIZED);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* check_asym_packing - Check to see if the group is packed into the
|
|
* sched domain.
|
|
*
|
|
* This is primarily intended to used at the sibling level. Some
|
|
* cores like POWER7 prefer to use lower numbered SMT threads. In the
|
|
* case of POWER7, it can move to lower SMT modes only when higher
|
|
* threads are idle. When in lower SMT modes, the threads will
|
|
* perform better since they share less core resources. Hence when we
|
|
* have idle threads, we want them to be the higher ones.
|
|
*
|
|
* This packing function is run on idle threads. It checks to see if
|
|
* the busiest CPU in this domain (core in the P7 case) has a higher
|
|
* CPU number than the packing function is being run on. Here we are
|
|
* assuming lower CPU number will be equivalent to lower a SMT thread
|
|
* number.
|
|
*
|
|
* Return: 1 when packing is required and a task should be moved to
|
|
* this CPU. The amount of the imbalance is returned in env->imbalance.
|
|
*
|
|
* @env: The load balancing environment.
|
|
* @sds: Statistics of the sched_domain which is to be packed
|
|
*/
|
|
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
|
|
{
|
|
int busiest_cpu;
|
|
|
|
if (!(env->sd->flags & SD_ASYM_PACKING))
|
|
return 0;
|
|
|
|
if (env->idle == CPU_NOT_IDLE)
|
|
return 0;
|
|
|
|
if (!sds->busiest)
|
|
return 0;
|
|
|
|
busiest_cpu = sds->busiest->asym_prefer_cpu;
|
|
if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
|
|
return 0;
|
|
|
|
env->imbalance = sds->busiest_stat.group_load;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/**
|
|
* fix_small_imbalance - Calculate the minor imbalance that exists
|
|
* amongst the groups of a sched_domain, during
|
|
* load balancing.
|
|
* @env: The load balancing environment.
|
|
* @sds: Statistics of the sched_domain whose imbalance is to be calculated.
|
|
*/
|
|
static inline
|
|
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
|
|
{
|
|
unsigned long tmp, capa_now = 0, capa_move = 0;
|
|
unsigned int imbn = 2;
|
|
unsigned long scaled_busy_load_per_task;
|
|
struct sg_lb_stats *local, *busiest;
|
|
|
|
local = &sds->local_stat;
|
|
busiest = &sds->busiest_stat;
|
|
|
|
if (!local->sum_nr_running)
|
|
local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
|
|
else if (busiest->load_per_task > local->load_per_task)
|
|
imbn = 1;
|
|
|
|
scaled_busy_load_per_task =
|
|
(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
|
|
busiest->group_capacity;
|
|
|
|
if (busiest->avg_load + scaled_busy_load_per_task >=
|
|
local->avg_load + (scaled_busy_load_per_task * imbn)) {
|
|
env->imbalance = busiest->load_per_task;
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* OK, we don't have enough imbalance to justify moving tasks,
|
|
* however we may be able to increase total CPU capacity used by
|
|
* moving them.
|
|
*/
|
|
|
|
capa_now += busiest->group_capacity *
|
|
min(busiest->load_per_task, busiest->avg_load);
|
|
capa_now += local->group_capacity *
|
|
min(local->load_per_task, local->avg_load);
|
|
capa_now /= SCHED_CAPACITY_SCALE;
|
|
|
|
/* Amount of load we'd subtract */
|
|
if (busiest->avg_load > scaled_busy_load_per_task) {
|
|
capa_move += busiest->group_capacity *
|
|
min(busiest->load_per_task,
|
|
busiest->avg_load - scaled_busy_load_per_task);
|
|
}
|
|
|
|
/* Amount of load we'd add */
|
|
if (busiest->avg_load * busiest->group_capacity <
|
|
busiest->load_per_task * SCHED_CAPACITY_SCALE) {
|
|
tmp = (busiest->avg_load * busiest->group_capacity) /
|
|
local->group_capacity;
|
|
} else {
|
|
tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
|
|
local->group_capacity;
|
|
}
|
|
capa_move += local->group_capacity *
|
|
min(local->load_per_task, local->avg_load + tmp);
|
|
capa_move /= SCHED_CAPACITY_SCALE;
|
|
|
|
/* Move if we gain throughput */
|
|
if (capa_move > capa_now)
|
|
env->imbalance = busiest->load_per_task;
|
|
}
|
|
|
|
/**
|
|
* calculate_imbalance - Calculate the amount of imbalance present within the
|
|
* groups of a given sched_domain during load balance.
|
|
* @env: load balance environment
|
|
* @sds: statistics of the sched_domain whose imbalance is to be calculated.
|
|
*/
|
|
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
|
|
{
|
|
unsigned long max_pull, load_above_capacity = ~0UL;
|
|
struct sg_lb_stats *local, *busiest;
|
|
|
|
local = &sds->local_stat;
|
|
busiest = &sds->busiest_stat;
|
|
|
|
if (busiest->group_type == group_imbalanced) {
|
|
/*
|
|
* In the group_imb case we cannot rely on group-wide averages
|
|
* to ensure CPU-load equilibrium, look at wider averages. XXX
|
|
*/
|
|
busiest->load_per_task =
|
|
min(busiest->load_per_task, sds->avg_load);
|
|
}
|
|
|
|
/*
|
|
* Avg load of busiest sg can be less and avg load of local sg can
|
|
* be greater than avg load across all sgs of sd because avg load
|
|
* factors in sg capacity and sgs with smaller group_type are
|
|
* skipped when updating the busiest sg:
|
|
*/
|
|
if (busiest->group_type != group_misfit_task &&
|
|
(busiest->avg_load <= sds->avg_load ||
|
|
local->avg_load >= sds->avg_load)) {
|
|
env->imbalance = 0;
|
|
return fix_small_imbalance(env, sds);
|
|
}
|
|
|
|
/*
|
|
* If there aren't any idle CPUs, avoid creating some.
|
|
*/
|
|
if (busiest->group_type == group_overloaded &&
|
|
local->group_type == group_overloaded) {
|
|
load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
|
|
if (load_above_capacity > busiest->group_capacity) {
|
|
load_above_capacity -= busiest->group_capacity;
|
|
load_above_capacity *= scale_load_down(NICE_0_LOAD);
|
|
load_above_capacity /= busiest->group_capacity;
|
|
} else
|
|
load_above_capacity = ~0UL;
|
|
}
|
|
|
|
/*
|
|
* We're trying to get all the CPUs to the average_load, so we don't
|
|
* want to push ourselves above the average load, nor do we wish to
|
|
* reduce the max loaded CPU below the average load. At the same time,
|
|
* we also don't want to reduce the group load below the group
|
|
* capacity. Thus we look for the minimum possible imbalance.
|
|
*/
|
|
max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
|
|
|
|
/* How much load to actually move to equalise the imbalance */
|
|
env->imbalance = min(
|
|
max_pull * busiest->group_capacity,
|
|
(sds->avg_load - local->avg_load) * local->group_capacity
|
|
) / SCHED_CAPACITY_SCALE;
|
|
|
|
/* Boost imbalance to allow misfit task to be balanced. */
|
|
if (busiest->group_type == group_misfit_task) {
|
|
env->imbalance = max_t(long, env->imbalance,
|
|
busiest->group_misfit_task_load);
|
|
}
|
|
|
|
/*
|
|
* if *imbalance is less than the average load per runnable task
|
|
* there is no guarantee that any tasks will be moved so we'll have
|
|
* a think about bumping its value to force at least one task to be
|
|
* moved
|
|
*/
|
|
if (env->imbalance < busiest->load_per_task)
|
|
return fix_small_imbalance(env, sds);
|
|
}
|
|
|
|
/******* find_busiest_group() helpers end here *********************/
|
|
|
|
/**
|
|
* find_busiest_group - Returns the busiest group within the sched_domain
|
|
* if there is an imbalance.
|
|
*
|
|
* Also calculates the amount of weighted load which should be moved
|
|
* to restore balance.
|
|
*
|
|
* @env: The load balancing environment.
|
|
*
|
|
* Return: - The busiest group if imbalance exists.
|
|
*/
|
|
static struct sched_group *find_busiest_group(struct lb_env *env)
|
|
{
|
|
struct sg_lb_stats *local, *busiest;
|
|
struct sd_lb_stats sds;
|
|
|
|
init_sd_lb_stats(&sds);
|
|
|
|
/*
|
|
* Compute the various statistics relavent for load balancing at
|
|
* this level.
|
|
*/
|
|
update_sd_lb_stats(env, &sds);
|
|
|
|
if (sched_energy_enabled()) {
|
|
struct root_domain *rd = env->dst_rq->rd;
|
|
|
|
if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
|
|
goto out_balanced;
|
|
}
|
|
|
|
local = &sds.local_stat;
|
|
busiest = &sds.busiest_stat;
|
|
|
|
/* ASYM feature bypasses nice load balance check */
|
|
if (check_asym_packing(env, &sds))
|
|
return sds.busiest;
|
|
|
|
/* There is no busy sibling group to pull tasks from */
|
|
if (!sds.busiest || busiest->sum_nr_running == 0)
|
|
goto out_balanced;
|
|
|
|
/* XXX broken for overlapping NUMA groups */
|
|
sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
|
|
/ sds.total_capacity;
|
|
|
|
/*
|
|
* If the busiest group is imbalanced the below checks don't
|
|
* work because they assume all things are equal, which typically
|
|
* isn't true due to cpus_allowed constraints and the like.
|
|
*/
|
|
if (busiest->group_type == group_imbalanced)
|
|
goto force_balance;
|
|
|
|
/*
|
|
* When dst_cpu is idle, prevent SMP nice and/or asymmetric group
|
|
* capacities from resulting in underutilization due to avg_load.
|
|
*/
|
|
if (env->idle != CPU_NOT_IDLE && group_has_capacity(env, local) &&
|
|
busiest->group_no_capacity)
|
|
goto force_balance;
|
|
|
|
/* Misfit tasks should be dealt with regardless of the avg load */
|
|
if (busiest->group_type == group_misfit_task)
|
|
goto force_balance;
|
|
|
|
/*
|
|
* If the local group is busier than the selected busiest group
|
|
* don't try and pull any tasks.
|
|
*/
|
|
if (local->avg_load >= busiest->avg_load)
|
|
goto out_balanced;
|
|
|
|
/*
|
|
* Don't pull any tasks if this group is already above the domain
|
|
* average load.
|
|
*/
|
|
if (local->avg_load >= sds.avg_load)
|
|
goto out_balanced;
|
|
|
|
if (env->idle == CPU_IDLE) {
|
|
/*
|
|
* This CPU is idle. If the busiest group is not overloaded
|
|
* and there is no imbalance between this and busiest group
|
|
* wrt idle CPUs, it is balanced. The imbalance becomes
|
|
* significant if the diff is greater than 1 otherwise we
|
|
* might end up to just move the imbalance on another group
|
|
*/
|
|
if ((busiest->group_type != group_overloaded) &&
|
|
(local->idle_cpus <= (busiest->idle_cpus + 1)))
|
|
goto out_balanced;
|
|
} else {
|
|
/*
|
|
* In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
|
|
* imbalance_pct to be conservative.
|
|
*/
|
|
if (100 * busiest->avg_load <=
|
|
env->sd->imbalance_pct * local->avg_load)
|
|
goto out_balanced;
|
|
}
|
|
|
|
force_balance:
|
|
/* Looks like there is an imbalance. Compute it */
|
|
env->src_grp_type = busiest->group_type;
|
|
calculate_imbalance(env, &sds);
|
|
return env->imbalance ? sds.busiest : NULL;
|
|
|
|
out_balanced:
|
|
env->imbalance = 0;
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* find_busiest_queue - find the busiest runqueue among the CPUs in the group.
|
|
*/
|
|
static struct rq *find_busiest_queue(struct lb_env *env,
|
|
struct sched_group *group)
|
|
{
|
|
struct rq *busiest = NULL, *rq;
|
|
unsigned long busiest_load = 0, busiest_capacity = 1;
|
|
int i;
|
|
|
|
for_each_cpu_and(i, sched_group_span(group), env->cpus) {
|
|
unsigned long capacity, wl;
|
|
enum fbq_type rt;
|
|
|
|
rq = cpu_rq(i);
|
|
rt = fbq_classify_rq(rq);
|
|
|
|
/*
|
|
* We classify groups/runqueues into three groups:
|
|
* - regular: there are !numa tasks
|
|
* - remote: there are numa tasks that run on the 'wrong' node
|
|
* - all: there is no distinction
|
|
*
|
|
* In order to avoid migrating ideally placed numa tasks,
|
|
* ignore those when there's better options.
|
|
*
|
|
* If we ignore the actual busiest queue to migrate another
|
|
* task, the next balance pass can still reduce the busiest
|
|
* queue by moving tasks around inside the node.
|
|
*
|
|
* If we cannot move enough load due to this classification
|
|
* the next pass will adjust the group classification and
|
|
* allow migration of more tasks.
|
|
*
|
|
* Both cases only affect the total convergence complexity.
|
|
*/
|
|
if (rt > env->fbq_type)
|
|
continue;
|
|
|
|
/*
|
|
* For ASYM_CPUCAPACITY domains with misfit tasks we simply
|
|
* seek the "biggest" misfit task.
|
|
*/
|
|
if (env->src_grp_type == group_misfit_task) {
|
|
if (rq->misfit_task_load > busiest_load) {
|
|
busiest_load = rq->misfit_task_load;
|
|
busiest = rq;
|
|
}
|
|
|
|
continue;
|
|
}
|
|
|
|
capacity = capacity_of(i);
|
|
|
|
/*
|
|
* For ASYM_CPUCAPACITY domains, don't pick a CPU that could
|
|
* eventually lead to active_balancing high->low capacity.
|
|
* Higher per-CPU capacity is considered better than balancing
|
|
* average load.
|
|
*/
|
|
if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
|
|
capacity_of(env->dst_cpu) < capacity &&
|
|
rq->nr_running == 1)
|
|
continue;
|
|
|
|
wl = weighted_cpuload(rq);
|
|
|
|
/*
|
|
* When comparing with imbalance, use weighted_cpuload()
|
|
* which is not scaled with the CPU capacity.
|
|
*/
|
|
|
|
if (rq->nr_running == 1 && wl > env->imbalance &&
|
|
!check_cpu_capacity(rq, env->sd))
|
|
continue;
|
|
|
|
/*
|
|
* For the load comparisons with the other CPU's, consider
|
|
* the weighted_cpuload() scaled with the CPU capacity, so
|
|
* that the load can be moved away from the CPU that is
|
|
* potentially running at a lower capacity.
|
|
*
|
|
* Thus we're looking for max(wl_i / capacity_i), crosswise
|
|
* multiplication to rid ourselves of the division works out
|
|
* to: wl_i * capacity_j > wl_j * capacity_i; where j is
|
|
* our previous maximum.
|
|
*/
|
|
if (wl * busiest_capacity > busiest_load * capacity) {
|
|
busiest_load = wl;
|
|
busiest_capacity = capacity;
|
|
busiest = rq;
|
|
}
|
|
}
|
|
|
|
return busiest;
|
|
}
|
|
|
|
/*
|
|
* Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
|
|
* so long as it is large enough.
|
|
*/
|
|
#define MAX_PINNED_INTERVAL 512
|
|
|
|
static inline bool
|
|
asym_active_balance(struct lb_env *env)
|
|
{
|
|
/*
|
|
* ASYM_PACKING needs to force migrate tasks from busy but
|
|
* lower priority CPUs in order to pack all tasks in the
|
|
* highest priority CPUs.
|
|
*/
|
|
return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
|
|
sched_asym_prefer(env->dst_cpu, env->src_cpu);
|
|
}
|
|
|
|
static inline bool
|
|
voluntary_active_balance(struct lb_env *env)
|
|
{
|
|
struct sched_domain *sd = env->sd;
|
|
|
|
if (asym_active_balance(env))
|
|
return 1;
|
|
|
|
/*
|
|
* The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
|
|
* It's worth migrating the task if the src_cpu's capacity is reduced
|
|
* because of other sched_class or IRQs if more capacity stays
|
|
* available on dst_cpu.
|
|
*/
|
|
if ((env->idle != CPU_NOT_IDLE) &&
|
|
(env->src_rq->cfs.h_nr_running == 1)) {
|
|
if ((check_cpu_capacity(env->src_rq, sd)) &&
|
|
(capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
|
|
return 1;
|
|
}
|
|
|
|
if (env->src_grp_type == group_misfit_task)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int need_active_balance(struct lb_env *env)
|
|
{
|
|
struct sched_domain *sd = env->sd;
|
|
|
|
if (voluntary_active_balance(env))
|
|
return 1;
|
|
|
|
return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
|
|
}
|
|
|
|
static int active_load_balance_cpu_stop(void *data);
|
|
|
|
static int should_we_balance(struct lb_env *env)
|
|
{
|
|
struct sched_group *sg = env->sd->groups;
|
|
int cpu, balance_cpu = -1;
|
|
|
|
/*
|
|
* Ensure the balancing environment is consistent; can happen
|
|
* when the softirq triggers 'during' hotplug.
|
|
*/
|
|
if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
|
|
return 0;
|
|
|
|
/*
|
|
* In the newly idle case, we will allow all the CPUs
|
|
* to do the newly idle load balance.
|
|
*/
|
|
if (env->idle == CPU_NEWLY_IDLE)
|
|
return 1;
|
|
|
|
/* Try to find first idle CPU */
|
|
for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
|
|
if (!idle_cpu(cpu))
|
|
continue;
|
|
|
|
balance_cpu = cpu;
|
|
break;
|
|
}
|
|
|
|
if (balance_cpu == -1)
|
|
balance_cpu = group_balance_cpu(sg);
|
|
|
|
/*
|
|
* First idle CPU or the first CPU(busiest) in this sched group
|
|
* is eligible for doing load balancing at this and above domains.
|
|
*/
|
|
return balance_cpu == env->dst_cpu;
|
|
}
|
|
|
|
/*
|
|
* Check this_cpu to ensure it is balanced within domain. Attempt to move
|
|
* tasks if there is an imbalance.
|
|
*/
|
|
static int load_balance(int this_cpu, struct rq *this_rq,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *continue_balancing)
|
|
{
|
|
int ld_moved, cur_ld_moved, active_balance = 0;
|
|
struct sched_domain *sd_parent = sd->parent;
|
|
struct sched_group *group;
|
|
struct rq *busiest;
|
|
struct rq_flags rf;
|
|
struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
|
|
|
|
struct lb_env env = {
|
|
.sd = sd,
|
|
.dst_cpu = this_cpu,
|
|
.dst_rq = this_rq,
|
|
.dst_grpmask = sched_group_span(sd->groups),
|
|
.idle = idle,
|
|
.loop_break = sched_nr_migrate_break,
|
|
.cpus = cpus,
|
|
.fbq_type = all,
|
|
.tasks = LIST_HEAD_INIT(env.tasks),
|
|
};
|
|
|
|
cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
|
|
|
|
schedstat_inc(sd->lb_count[idle]);
|
|
|
|
redo:
|
|
if (!should_we_balance(&env)) {
|
|
*continue_balancing = 0;
|
|
goto out_balanced;
|
|
}
|
|
|
|
group = find_busiest_group(&env);
|
|
if (!group) {
|
|
schedstat_inc(sd->lb_nobusyg[idle]);
|
|
goto out_balanced;
|
|
}
|
|
|
|
busiest = find_busiest_queue(&env, group);
|
|
if (!busiest) {
|
|
schedstat_inc(sd->lb_nobusyq[idle]);
|
|
goto out_balanced;
|
|
}
|
|
|
|
BUG_ON(busiest == env.dst_rq);
|
|
|
|
schedstat_add(sd->lb_imbalance[idle], env.imbalance);
|
|
|
|
env.src_cpu = busiest->cpu;
|
|
env.src_rq = busiest;
|
|
|
|
ld_moved = 0;
|
|
if (busiest->nr_running > 1) {
|
|
/*
|
|
* Attempt to move tasks. If find_busiest_group has found
|
|
* an imbalance but busiest->nr_running <= 1, the group is
|
|
* still unbalanced. ld_moved simply stays zero, so it is
|
|
* correctly treated as an imbalance.
|
|
*/
|
|
env.flags |= LBF_ALL_PINNED;
|
|
env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
|
|
|
|
more_balance:
|
|
rq_lock_irqsave(busiest, &rf);
|
|
update_rq_clock(busiest);
|
|
|
|
/*
|
|
* cur_ld_moved - load moved in current iteration
|
|
* ld_moved - cumulative load moved across iterations
|
|
*/
|
|
cur_ld_moved = detach_tasks(&env);
|
|
|
|
/*
|
|
* We've detached some tasks from busiest_rq. Every
|
|
* task is masked "TASK_ON_RQ_MIGRATING", so we can safely
|
|
* unlock busiest->lock, and we are able to be sure
|
|
* that nobody can manipulate the tasks in parallel.
|
|
* See task_rq_lock() family for the details.
|
|
*/
|
|
|
|
rq_unlock(busiest, &rf);
|
|
|
|
if (cur_ld_moved) {
|
|
attach_tasks(&env);
|
|
ld_moved += cur_ld_moved;
|
|
}
|
|
|
|
local_irq_restore(rf.flags);
|
|
|
|
if (env.flags & LBF_NEED_BREAK) {
|
|
env.flags &= ~LBF_NEED_BREAK;
|
|
goto more_balance;
|
|
}
|
|
|
|
/*
|
|
* Revisit (affine) tasks on src_cpu that couldn't be moved to
|
|
* us and move them to an alternate dst_cpu in our sched_group
|
|
* where they can run. The upper limit on how many times we
|
|
* iterate on same src_cpu is dependent on number of CPUs in our
|
|
* sched_group.
|
|
*
|
|
* This changes load balance semantics a bit on who can move
|
|
* load to a given_cpu. In addition to the given_cpu itself
|
|
* (or a ilb_cpu acting on its behalf where given_cpu is
|
|
* nohz-idle), we now have balance_cpu in a position to move
|
|
* load to given_cpu. In rare situations, this may cause
|
|
* conflicts (balance_cpu and given_cpu/ilb_cpu deciding
|
|
* _independently_ and at _same_ time to move some load to
|
|
* given_cpu) causing exceess load to be moved to given_cpu.
|
|
* This however should not happen so much in practice and
|
|
* moreover subsequent load balance cycles should correct the
|
|
* excess load moved.
|
|
*/
|
|
if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
|
|
|
|
/* Prevent to re-select dst_cpu via env's CPUs */
|
|
__cpumask_clear_cpu(env.dst_cpu, env.cpus);
|
|
|
|
env.dst_rq = cpu_rq(env.new_dst_cpu);
|
|
env.dst_cpu = env.new_dst_cpu;
|
|
env.flags &= ~LBF_DST_PINNED;
|
|
env.loop = 0;
|
|
env.loop_break = sched_nr_migrate_break;
|
|
|
|
/*
|
|
* Go back to "more_balance" rather than "redo" since we
|
|
* need to continue with same src_cpu.
|
|
*/
|
|
goto more_balance;
|
|
}
|
|
|
|
/*
|
|
* We failed to reach balance because of affinity.
|
|
*/
|
|
if (sd_parent) {
|
|
int *group_imbalance = &sd_parent->groups->sgc->imbalance;
|
|
|
|
if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
|
|
*group_imbalance = 1;
|
|
}
|
|
|
|
/* All tasks on this runqueue were pinned by CPU affinity */
|
|
if (unlikely(env.flags & LBF_ALL_PINNED)) {
|
|
__cpumask_clear_cpu(cpu_of(busiest), cpus);
|
|
/*
|
|
* Attempting to continue load balancing at the current
|
|
* sched_domain level only makes sense if there are
|
|
* active CPUs remaining as possible busiest CPUs to
|
|
* pull load from which are not contained within the
|
|
* destination group that is receiving any migrated
|
|
* load.
|
|
*/
|
|
if (!cpumask_subset(cpus, env.dst_grpmask)) {
|
|
env.loop = 0;
|
|
env.loop_break = sched_nr_migrate_break;
|
|
goto redo;
|
|
}
|
|
goto out_all_pinned;
|
|
}
|
|
}
|
|
|
|
if (!ld_moved) {
|
|
schedstat_inc(sd->lb_failed[idle]);
|
|
/*
|
|
* Increment the failure counter only on periodic balance.
|
|
* We do not want newidle balance, which can be very
|
|
* frequent, pollute the failure counter causing
|
|
* excessive cache_hot migrations and active balances.
|
|
*/
|
|
if (idle != CPU_NEWLY_IDLE)
|
|
sd->nr_balance_failed++;
|
|
|
|
if (need_active_balance(&env)) {
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&busiest->lock, flags);
|
|
|
|
/*
|
|
* Don't kick the active_load_balance_cpu_stop,
|
|
* if the curr task on busiest CPU can't be
|
|
* moved to this_cpu:
|
|
*/
|
|
if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
|
|
raw_spin_unlock_irqrestore(&busiest->lock,
|
|
flags);
|
|
env.flags |= LBF_ALL_PINNED;
|
|
goto out_one_pinned;
|
|
}
|
|
|
|
/*
|
|
* ->active_balance synchronizes accesses to
|
|
* ->active_balance_work. Once set, it's cleared
|
|
* only after active load balance is finished.
|
|
*/
|
|
if (!busiest->active_balance) {
|
|
busiest->active_balance = 1;
|
|
busiest->push_cpu = this_cpu;
|
|
active_balance = 1;
|
|
}
|
|
raw_spin_unlock_irqrestore(&busiest->lock, flags);
|
|
|
|
if (active_balance) {
|
|
stop_one_cpu_nowait(cpu_of(busiest),
|
|
active_load_balance_cpu_stop, busiest,
|
|
&busiest->active_balance_work);
|
|
}
|
|
|
|
/* We've kicked active balancing, force task migration. */
|
|
sd->nr_balance_failed = sd->cache_nice_tries+1;
|
|
}
|
|
} else
|
|
sd->nr_balance_failed = 0;
|
|
|
|
if (likely(!active_balance) || voluntary_active_balance(&env)) {
|
|
/* We were unbalanced, so reset the balancing interval */
|
|
sd->balance_interval = sd->min_interval;
|
|
} else {
|
|
/*
|
|
* If we've begun active balancing, start to back off. This
|
|
* case may not be covered by the all_pinned logic if there
|
|
* is only 1 task on the busy runqueue (because we don't call
|
|
* detach_tasks).
|
|
*/
|
|
if (sd->balance_interval < sd->max_interval)
|
|
sd->balance_interval *= 2;
|
|
}
|
|
|
|
goto out;
|
|
|
|
out_balanced:
|
|
/*
|
|
* We reach balance although we may have faced some affinity
|
|
* constraints. Clear the imbalance flag if it was set.
|
|
*/
|
|
if (sd_parent) {
|
|
int *group_imbalance = &sd_parent->groups->sgc->imbalance;
|
|
|
|
if (*group_imbalance)
|
|
*group_imbalance = 0;
|
|
}
|
|
|
|
out_all_pinned:
|
|
/*
|
|
* We reach balance because all tasks are pinned at this level so
|
|
* we can't migrate them. Let the imbalance flag set so parent level
|
|
* can try to migrate them.
|
|
*/
|
|
schedstat_inc(sd->lb_balanced[idle]);
|
|
|
|
sd->nr_balance_failed = 0;
|
|
|
|
out_one_pinned:
|
|
ld_moved = 0;
|
|
|
|
/*
|
|
* idle_balance() disregards balance intervals, so we could repeatedly
|
|
* reach this code, which would lead to balance_interval skyrocketting
|
|
* in a short amount of time. Skip the balance_interval increase logic
|
|
* to avoid that.
|
|
*/
|
|
if (env.idle == CPU_NEWLY_IDLE)
|
|
goto out;
|
|
|
|
/* tune up the balancing interval */
|
|
if ((env.flags & LBF_ALL_PINNED &&
|
|
sd->balance_interval < MAX_PINNED_INTERVAL) ||
|
|
sd->balance_interval < sd->max_interval)
|
|
sd->balance_interval *= 2;
|
|
out:
|
|
return ld_moved;
|
|
}
|
|
|
|
static inline unsigned long
|
|
get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
|
|
{
|
|
unsigned long interval = sd->balance_interval;
|
|
|
|
if (cpu_busy)
|
|
interval *= sd->busy_factor;
|
|
|
|
/* scale ms to jiffies */
|
|
interval = msecs_to_jiffies(interval);
|
|
interval = clamp(interval, 1UL, max_load_balance_interval);
|
|
|
|
return interval;
|
|
}
|
|
|
|
static inline void
|
|
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
|
|
{
|
|
unsigned long interval, next;
|
|
|
|
/* used by idle balance, so cpu_busy = 0 */
|
|
interval = get_sd_balance_interval(sd, 0);
|
|
next = sd->last_balance + interval;
|
|
|
|
if (time_after(*next_balance, next))
|
|
*next_balance = next;
|
|
}
|
|
|
|
/*
|
|
* active_load_balance_cpu_stop is run by the CPU stopper. It pushes
|
|
* running tasks off the busiest CPU onto idle CPUs. It requires at
|
|
* least 1 task to be running on each physical CPU where possible, and
|
|
* avoids physical / logical imbalances.
|
|
*/
|
|
static int active_load_balance_cpu_stop(void *data)
|
|
{
|
|
struct rq *busiest_rq = data;
|
|
int busiest_cpu = cpu_of(busiest_rq);
|
|
int target_cpu = busiest_rq->push_cpu;
|
|
struct rq *target_rq = cpu_rq(target_cpu);
|
|
struct sched_domain *sd;
|
|
struct task_struct *p = NULL;
|
|
struct rq_flags rf;
|
|
|
|
rq_lock_irq(busiest_rq, &rf);
|
|
/*
|
|
* Between queueing the stop-work and running it is a hole in which
|
|
* CPUs can become inactive. We should not move tasks from or to
|
|
* inactive CPUs.
|
|
*/
|
|
if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
|
|
goto out_unlock;
|
|
|
|
/* Make sure the requested CPU hasn't gone down in the meantime: */
|
|
if (unlikely(busiest_cpu != smp_processor_id() ||
|
|
!busiest_rq->active_balance))
|
|
goto out_unlock;
|
|
|
|
/* Is there any task to move? */
|
|
if (busiest_rq->nr_running <= 1)
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* This condition is "impossible", if it occurs
|
|
* we need to fix it. Originally reported by
|
|
* Bjorn Helgaas on a 128-CPU setup.
|
|
*/
|
|
BUG_ON(busiest_rq == target_rq);
|
|
|
|
/* Search for an sd spanning us and the target CPU. */
|
|
rcu_read_lock();
|
|
for_each_domain(target_cpu, sd) {
|
|
if ((sd->flags & SD_LOAD_BALANCE) &&
|
|
cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
|
|
break;
|
|
}
|
|
|
|
if (likely(sd)) {
|
|
struct lb_env env = {
|
|
.sd = sd,
|
|
.dst_cpu = target_cpu,
|
|
.dst_rq = target_rq,
|
|
.src_cpu = busiest_rq->cpu,
|
|
.src_rq = busiest_rq,
|
|
.idle = CPU_IDLE,
|
|
/*
|
|
* can_migrate_task() doesn't need to compute new_dst_cpu
|
|
* for active balancing. Since we have CPU_IDLE, but no
|
|
* @dst_grpmask we need to make that test go away with lying
|
|
* about DST_PINNED.
|
|
*/
|
|
.flags = LBF_DST_PINNED,
|
|
};
|
|
|
|
schedstat_inc(sd->alb_count);
|
|
update_rq_clock(busiest_rq);
|
|
|
|
p = detach_one_task(&env);
|
|
if (p) {
|
|
schedstat_inc(sd->alb_pushed);
|
|
/* Active balancing done, reset the failure counter. */
|
|
sd->nr_balance_failed = 0;
|
|
} else {
|
|
schedstat_inc(sd->alb_failed);
|
|
}
|
|
}
|
|
rcu_read_unlock();
|
|
out_unlock:
|
|
busiest_rq->active_balance = 0;
|
|
rq_unlock(busiest_rq, &rf);
|
|
|
|
if (p)
|
|
attach_one_task(target_rq, p);
|
|
|
|
local_irq_enable();
|
|
|
|
return 0;
|
|
}
|
|
|
|
static DEFINE_SPINLOCK(balancing);
|
|
|
|
/*
|
|
* Scale the max load_balance interval with the number of CPUs in the system.
|
|
* This trades load-balance latency on larger machines for less cross talk.
|
|
*/
|
|
void update_max_interval(void)
|
|
{
|
|
max_load_balance_interval = HZ*num_online_cpus()/10;
|
|
}
|
|
|
|
/*
|
|
* It checks each scheduling domain to see if it is due to be balanced,
|
|
* and initiates a balancing operation if so.
|
|
*
|
|
* Balancing parameters are set up in init_sched_domains.
|
|
*/
|
|
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
|
|
{
|
|
int continue_balancing = 1;
|
|
int cpu = rq->cpu;
|
|
unsigned long interval;
|
|
struct sched_domain *sd;
|
|
/* Earliest time when we have to do rebalance again */
|
|
unsigned long next_balance = jiffies + 60*HZ;
|
|
int update_next_balance = 0;
|
|
int need_serialize, need_decay = 0;
|
|
u64 max_cost = 0;
|
|
|
|
rcu_read_lock();
|
|
for_each_domain(cpu, sd) {
|
|
/*
|
|
* Decay the newidle max times here because this is a regular
|
|
* visit to all the domains. Decay ~1% per second.
|
|
*/
|
|
if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
|
|
sd->max_newidle_lb_cost =
|
|
(sd->max_newidle_lb_cost * 253) / 256;
|
|
sd->next_decay_max_lb_cost = jiffies + HZ;
|
|
need_decay = 1;
|
|
}
|
|
max_cost += sd->max_newidle_lb_cost;
|
|
|
|
if (!(sd->flags & SD_LOAD_BALANCE))
|
|
continue;
|
|
|
|
/*
|
|
* Stop the load balance at this level. There is another
|
|
* CPU in our sched group which is doing load balancing more
|
|
* actively.
|
|
*/
|
|
if (!continue_balancing) {
|
|
if (need_decay)
|
|
continue;
|
|
break;
|
|
}
|
|
|
|
interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
|
|
|
|
need_serialize = sd->flags & SD_SERIALIZE;
|
|
if (need_serialize) {
|
|
if (!spin_trylock(&balancing))
|
|
goto out;
|
|
}
|
|
|
|
if (time_after_eq(jiffies, sd->last_balance + interval)) {
|
|
if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
|
|
/*
|
|
* The LBF_DST_PINNED logic could have changed
|
|
* env->dst_cpu, so we can't know our idle
|
|
* state even if we migrated tasks. Update it.
|
|
*/
|
|
idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
|
|
}
|
|
sd->last_balance = jiffies;
|
|
interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
|
|
}
|
|
if (need_serialize)
|
|
spin_unlock(&balancing);
|
|
out:
|
|
if (time_after(next_balance, sd->last_balance + interval)) {
|
|
next_balance = sd->last_balance + interval;
|
|
update_next_balance = 1;
|
|
}
|
|
}
|
|
if (need_decay) {
|
|
/*
|
|
* Ensure the rq-wide value also decays but keep it at a
|
|
* reasonable floor to avoid funnies with rq->avg_idle.
|
|
*/
|
|
rq->max_idle_balance_cost =
|
|
max((u64)sysctl_sched_migration_cost, max_cost);
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* next_balance will be updated only when there is a need.
|
|
* When the cpu is attached to null domain for ex, it will not be
|
|
* updated.
|
|
*/
|
|
if (likely(update_next_balance)) {
|
|
rq->next_balance = next_balance;
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
/*
|
|
* If this CPU has been elected to perform the nohz idle
|
|
* balance. Other idle CPUs have already rebalanced with
|
|
* nohz_idle_balance() and nohz.next_balance has been
|
|
* updated accordingly. This CPU is now running the idle load
|
|
* balance for itself and we need to update the
|
|
* nohz.next_balance accordingly.
|
|
*/
|
|
if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
|
|
nohz.next_balance = rq->next_balance;
|
|
#endif
|
|
}
|
|
}
|
|
|
|
static inline int on_null_domain(struct rq *rq)
|
|
{
|
|
return unlikely(!rcu_dereference_sched(rq->sd));
|
|
}
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
/*
|
|
* idle load balancing details
|
|
* - When one of the busy CPUs notice that there may be an idle rebalancing
|
|
* needed, they will kick the idle load balancer, which then does idle
|
|
* load balancing for all the idle CPUs.
|
|
*/
|
|
|
|
static inline int find_new_ilb(void)
|
|
{
|
|
int ilb = cpumask_first(nohz.idle_cpus_mask);
|
|
|
|
if (ilb < nr_cpu_ids && idle_cpu(ilb))
|
|
return ilb;
|
|
|
|
return nr_cpu_ids;
|
|
}
|
|
|
|
/*
|
|
* Kick a CPU to do the nohz balancing, if it is time for it. We pick the
|
|
* nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
|
|
* CPU (if there is one).
|
|
*/
|
|
static void kick_ilb(unsigned int flags)
|
|
{
|
|
int ilb_cpu;
|
|
|
|
nohz.next_balance++;
|
|
|
|
ilb_cpu = find_new_ilb();
|
|
|
|
if (ilb_cpu >= nr_cpu_ids)
|
|
return;
|
|
|
|
flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
|
|
if (flags & NOHZ_KICK_MASK)
|
|
return;
|
|
|
|
/*
|
|
* Use smp_send_reschedule() instead of resched_cpu().
|
|
* This way we generate a sched IPI on the target CPU which
|
|
* is idle. And the softirq performing nohz idle load balance
|
|
* will be run before returning from the IPI.
|
|
*/
|
|
smp_send_reschedule(ilb_cpu);
|
|
}
|
|
|
|
/*
|
|
* Current decision point for kicking the idle load balancer in the presence
|
|
* of idle CPUs in the system.
|
|
*/
|
|
static void nohz_balancer_kick(struct rq *rq)
|
|
{
|
|
unsigned long now = jiffies;
|
|
struct sched_domain_shared *sds;
|
|
struct sched_domain *sd;
|
|
int nr_busy, i, cpu = rq->cpu;
|
|
unsigned int flags = 0;
|
|
|
|
if (unlikely(rq->idle_balance))
|
|
return;
|
|
|
|
/*
|
|
* We may be recently in ticked or tickless idle mode. At the first
|
|
* busy tick after returning from idle, we will update the busy stats.
|
|
*/
|
|
nohz_balance_exit_idle(rq);
|
|
|
|
/*
|
|
* None are in tickless mode and hence no need for NOHZ idle load
|
|
* balancing.
|
|
*/
|
|
if (likely(!atomic_read(&nohz.nr_cpus)))
|
|
return;
|
|
|
|
if (READ_ONCE(nohz.has_blocked) &&
|
|
time_after(now, READ_ONCE(nohz.next_blocked)))
|
|
flags = NOHZ_STATS_KICK;
|
|
|
|
if (time_before(now, nohz.next_balance))
|
|
goto out;
|
|
|
|
if (rq->nr_running >= 2) {
|
|
flags = NOHZ_KICK_MASK;
|
|
goto out;
|
|
}
|
|
|
|
rcu_read_lock();
|
|
|
|
sd = rcu_dereference(rq->sd);
|
|
if (sd) {
|
|
/*
|
|
* If there's a CFS task and the current CPU has reduced
|
|
* capacity; kick the ILB to see if there's a better CPU to run
|
|
* on.
|
|
*/
|
|
if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
|
|
flags = NOHZ_KICK_MASK;
|
|
goto unlock;
|
|
}
|
|
}
|
|
|
|
sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
|
|
if (sd) {
|
|
/*
|
|
* When ASYM_PACKING; see if there's a more preferred CPU
|
|
* currently idle; in which case, kick the ILB to move tasks
|
|
* around.
|
|
*/
|
|
for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
|
|
if (sched_asym_prefer(i, cpu)) {
|
|
flags = NOHZ_KICK_MASK;
|
|
goto unlock;
|
|
}
|
|
}
|
|
}
|
|
|
|
sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
|
|
if (sd) {
|
|
/*
|
|
* When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
|
|
* to run the misfit task on.
|
|
*/
|
|
if (check_misfit_status(rq, sd)) {
|
|
flags = NOHZ_KICK_MASK;
|
|
goto unlock;
|
|
}
|
|
|
|
/*
|
|
* For asymmetric systems, we do not want to nicely balance
|
|
* cache use, instead we want to embrace asymmetry and only
|
|
* ensure tasks have enough CPU capacity.
|
|
*
|
|
* Skip the LLC logic because it's not relevant in that case.
|
|
*/
|
|
goto unlock;
|
|
}
|
|
|
|
sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
|
|
if (sds) {
|
|
/*
|
|
* If there is an imbalance between LLC domains (IOW we could
|
|
* increase the overall cache use), we need some less-loaded LLC
|
|
* domain to pull some load. Likewise, we may need to spread
|
|
* load within the current LLC domain (e.g. packed SMT cores but
|
|
* other CPUs are idle). We can't really know from here how busy
|
|
* the others are - so just get a nohz balance going if it looks
|
|
* like this LLC domain has tasks we could move.
|
|
*/
|
|
nr_busy = atomic_read(&sds->nr_busy_cpus);
|
|
if (nr_busy > 1) {
|
|
flags = NOHZ_KICK_MASK;
|
|
goto unlock;
|
|
}
|
|
}
|
|
unlock:
|
|
rcu_read_unlock();
|
|
out:
|
|
if (flags)
|
|
kick_ilb(flags);
|
|
}
|
|
|
|
static void set_cpu_sd_state_busy(int cpu)
|
|
{
|
|
struct sched_domain *sd;
|
|
|
|
rcu_read_lock();
|
|
sd = rcu_dereference(per_cpu(sd_llc, cpu));
|
|
|
|
if (!sd || !sd->nohz_idle)
|
|
goto unlock;
|
|
sd->nohz_idle = 0;
|
|
|
|
atomic_inc(&sd->shared->nr_busy_cpus);
|
|
unlock:
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
void nohz_balance_exit_idle(struct rq *rq)
|
|
{
|
|
SCHED_WARN_ON(rq != this_rq());
|
|
|
|
if (likely(!rq->nohz_tick_stopped))
|
|
return;
|
|
|
|
rq->nohz_tick_stopped = 0;
|
|
cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
|
|
atomic_dec(&nohz.nr_cpus);
|
|
|
|
set_cpu_sd_state_busy(rq->cpu);
|
|
}
|
|
|
|
static void set_cpu_sd_state_idle(int cpu)
|
|
{
|
|
struct sched_domain *sd;
|
|
|
|
rcu_read_lock();
|
|
sd = rcu_dereference(per_cpu(sd_llc, cpu));
|
|
|
|
if (!sd || sd->nohz_idle)
|
|
goto unlock;
|
|
sd->nohz_idle = 1;
|
|
|
|
atomic_dec(&sd->shared->nr_busy_cpus);
|
|
unlock:
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/*
|
|
* This routine will record that the CPU is going idle with tick stopped.
|
|
* This info will be used in performing idle load balancing in the future.
|
|
*/
|
|
void nohz_balance_enter_idle(int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
|
|
SCHED_WARN_ON(cpu != smp_processor_id());
|
|
|
|
/* If this CPU is going down, then nothing needs to be done: */
|
|
if (!cpu_active(cpu))
|
|
return;
|
|
|
|
/* Spare idle load balancing on CPUs that don't want to be disturbed: */
|
|
if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
|
|
return;
|
|
|
|
/*
|
|
* Can be set safely without rq->lock held
|
|
* If a clear happens, it will have evaluated last additions because
|
|
* rq->lock is held during the check and the clear
|
|
*/
|
|
rq->has_blocked_load = 1;
|
|
|
|
/*
|
|
* The tick is still stopped but load could have been added in the
|
|
* meantime. We set the nohz.has_blocked flag to trig a check of the
|
|
* *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
|
|
* of nohz.has_blocked can only happen after checking the new load
|
|
*/
|
|
if (rq->nohz_tick_stopped)
|
|
goto out;
|
|
|
|
/* If we're a completely isolated CPU, we don't play: */
|
|
if (on_null_domain(rq))
|
|
return;
|
|
|
|
rq->nohz_tick_stopped = 1;
|
|
|
|
cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
|
|
atomic_inc(&nohz.nr_cpus);
|
|
|
|
/*
|
|
* Ensures that if nohz_idle_balance() fails to observe our
|
|
* @idle_cpus_mask store, it must observe the @has_blocked
|
|
* store.
|
|
*/
|
|
smp_mb__after_atomic();
|
|
|
|
set_cpu_sd_state_idle(cpu);
|
|
|
|
out:
|
|
/*
|
|
* Each time a cpu enter idle, we assume that it has blocked load and
|
|
* enable the periodic update of the load of idle cpus
|
|
*/
|
|
WRITE_ONCE(nohz.has_blocked, 1);
|
|
}
|
|
|
|
/*
|
|
* Internal function that runs load balance for all idle cpus. The load balance
|
|
* can be a simple update of blocked load or a complete load balance with
|
|
* tasks movement depending of flags.
|
|
* The function returns false if the loop has stopped before running
|
|
* through all idle CPUs.
|
|
*/
|
|
static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
|
|
enum cpu_idle_type idle)
|
|
{
|
|
/* Earliest time when we have to do rebalance again */
|
|
unsigned long now = jiffies;
|
|
unsigned long next_balance = now + 60*HZ;
|
|
bool has_blocked_load = false;
|
|
int update_next_balance = 0;
|
|
int this_cpu = this_rq->cpu;
|
|
int balance_cpu;
|
|
int ret = false;
|
|
struct rq *rq;
|
|
|
|
SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
|
|
|
|
/*
|
|
* We assume there will be no idle load after this update and clear
|
|
* the has_blocked flag. If a cpu enters idle in the mean time, it will
|
|
* set the has_blocked flag and trig another update of idle load.
|
|
* Because a cpu that becomes idle, is added to idle_cpus_mask before
|
|
* setting the flag, we are sure to not clear the state and not
|
|
* check the load of an idle cpu.
|
|
*/
|
|
WRITE_ONCE(nohz.has_blocked, 0);
|
|
|
|
/*
|
|
* Ensures that if we miss the CPU, we must see the has_blocked
|
|
* store from nohz_balance_enter_idle().
|
|
*/
|
|
smp_mb();
|
|
|
|
for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
|
|
if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
|
|
continue;
|
|
|
|
/*
|
|
* If this CPU gets work to do, stop the load balancing
|
|
* work being done for other CPUs. Next load
|
|
* balancing owner will pick it up.
|
|
*/
|
|
if (need_resched()) {
|
|
has_blocked_load = true;
|
|
goto abort;
|
|
}
|
|
|
|
rq = cpu_rq(balance_cpu);
|
|
|
|
has_blocked_load |= update_nohz_stats(rq, true);
|
|
|
|
/*
|
|
* If time for next balance is due,
|
|
* do the balance.
|
|
*/
|
|
if (time_after_eq(jiffies, rq->next_balance)) {
|
|
struct rq_flags rf;
|
|
|
|
rq_lock_irqsave(rq, &rf);
|
|
update_rq_clock(rq);
|
|
cpu_load_update_idle(rq);
|
|
rq_unlock_irqrestore(rq, &rf);
|
|
|
|
if (flags & NOHZ_BALANCE_KICK)
|
|
rebalance_domains(rq, CPU_IDLE);
|
|
}
|
|
|
|
if (time_after(next_balance, rq->next_balance)) {
|
|
next_balance = rq->next_balance;
|
|
update_next_balance = 1;
|
|
}
|
|
}
|
|
|
|
/* Newly idle CPU doesn't need an update */
|
|
if (idle != CPU_NEWLY_IDLE) {
|
|
update_blocked_averages(this_cpu);
|
|
has_blocked_load |= this_rq->has_blocked_load;
|
|
}
|
|
|
|
if (flags & NOHZ_BALANCE_KICK)
|
|
rebalance_domains(this_rq, CPU_IDLE);
|
|
|
|
WRITE_ONCE(nohz.next_blocked,
|
|
now + msecs_to_jiffies(LOAD_AVG_PERIOD));
|
|
|
|
/* The full idle balance loop has been done */
|
|
ret = true;
|
|
|
|
abort:
|
|
/* There is still blocked load, enable periodic update */
|
|
if (has_blocked_load)
|
|
WRITE_ONCE(nohz.has_blocked, 1);
|
|
|
|
/*
|
|
* next_balance will be updated only when there is a need.
|
|
* When the CPU is attached to null domain for ex, it will not be
|
|
* updated.
|
|
*/
|
|
if (likely(update_next_balance))
|
|
nohz.next_balance = next_balance;
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
|
|
* rebalancing for all the cpus for whom scheduler ticks are stopped.
|
|
*/
|
|
static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
|
|
{
|
|
int this_cpu = this_rq->cpu;
|
|
unsigned int flags;
|
|
|
|
if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK))
|
|
return false;
|
|
|
|
if (idle != CPU_IDLE) {
|
|
atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
|
|
return false;
|
|
}
|
|
|
|
/* could be _relaxed() */
|
|
flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
|
|
if (!(flags & NOHZ_KICK_MASK))
|
|
return false;
|
|
|
|
_nohz_idle_balance(this_rq, flags, idle);
|
|
|
|
return true;
|
|
}
|
|
|
|
static void nohz_newidle_balance(struct rq *this_rq)
|
|
{
|
|
int this_cpu = this_rq->cpu;
|
|
|
|
/*
|
|
* This CPU doesn't want to be disturbed by scheduler
|
|
* housekeeping
|
|
*/
|
|
if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED))
|
|
return;
|
|
|
|
/* Will wake up very soon. No time for doing anything else*/
|
|
if (this_rq->avg_idle < sysctl_sched_migration_cost)
|
|
return;
|
|
|
|
/* Don't need to update blocked load of idle CPUs*/
|
|
if (!READ_ONCE(nohz.has_blocked) ||
|
|
time_before(jiffies, READ_ONCE(nohz.next_blocked)))
|
|
return;
|
|
|
|
raw_spin_unlock(&this_rq->lock);
|
|
/*
|
|
* This CPU is going to be idle and blocked load of idle CPUs
|
|
* need to be updated. Run the ilb locally as it is a good
|
|
* candidate for ilb instead of waking up another idle CPU.
|
|
* Kick an normal ilb if we failed to do the update.
|
|
*/
|
|
if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE))
|
|
kick_ilb(NOHZ_STATS_KICK);
|
|
raw_spin_lock(&this_rq->lock);
|
|
}
|
|
|
|
#else /* !CONFIG_NO_HZ_COMMON */
|
|
static inline void nohz_balancer_kick(struct rq *rq) { }
|
|
|
|
static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
static inline void nohz_newidle_balance(struct rq *this_rq) { }
|
|
#endif /* CONFIG_NO_HZ_COMMON */
|
|
|
|
/*
|
|
* idle_balance is called by schedule() if this_cpu is about to become
|
|
* idle. Attempts to pull tasks from other CPUs.
|
|
*/
|
|
static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
|
|
{
|
|
unsigned long next_balance = jiffies + HZ;
|
|
int this_cpu = this_rq->cpu;
|
|
struct sched_domain *sd;
|
|
int pulled_task = 0;
|
|
u64 curr_cost = 0;
|
|
|
|
/*
|
|
* We must set idle_stamp _before_ calling idle_balance(), such that we
|
|
* measure the duration of idle_balance() as idle time.
|
|
*/
|
|
this_rq->idle_stamp = rq_clock(this_rq);
|
|
|
|
/*
|
|
* Do not pull tasks towards !active CPUs...
|
|
*/
|
|
if (!cpu_active(this_cpu))
|
|
return 0;
|
|
|
|
/*
|
|
* This is OK, because current is on_cpu, which avoids it being picked
|
|
* for load-balance and preemption/IRQs are still disabled avoiding
|
|
* further scheduler activity on it and we're being very careful to
|
|
* re-start the picking loop.
|
|
*/
|
|
rq_unpin_lock(this_rq, rf);
|
|
|
|
if (this_rq->avg_idle < sysctl_sched_migration_cost ||
|
|
!READ_ONCE(this_rq->rd->overload)) {
|
|
|
|
rcu_read_lock();
|
|
sd = rcu_dereference_check_sched_domain(this_rq->sd);
|
|
if (sd)
|
|
update_next_balance(sd, &next_balance);
|
|
rcu_read_unlock();
|
|
|
|
nohz_newidle_balance(this_rq);
|
|
|
|
goto out;
|
|
}
|
|
|
|
raw_spin_unlock(&this_rq->lock);
|
|
|
|
update_blocked_averages(this_cpu);
|
|
rcu_read_lock();
|
|
for_each_domain(this_cpu, sd) {
|
|
int continue_balancing = 1;
|
|
u64 t0, domain_cost;
|
|
|
|
if (!(sd->flags & SD_LOAD_BALANCE))
|
|
continue;
|
|
|
|
if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
|
|
update_next_balance(sd, &next_balance);
|
|
break;
|
|
}
|
|
|
|
if (sd->flags & SD_BALANCE_NEWIDLE) {
|
|
t0 = sched_clock_cpu(this_cpu);
|
|
|
|
pulled_task = load_balance(this_cpu, this_rq,
|
|
sd, CPU_NEWLY_IDLE,
|
|
&continue_balancing);
|
|
|
|
domain_cost = sched_clock_cpu(this_cpu) - t0;
|
|
if (domain_cost > sd->max_newidle_lb_cost)
|
|
sd->max_newidle_lb_cost = domain_cost;
|
|
|
|
curr_cost += domain_cost;
|
|
}
|
|
|
|
update_next_balance(sd, &next_balance);
|
|
|
|
/*
|
|
* Stop searching for tasks to pull if there are
|
|
* now runnable tasks on this rq.
|
|
*/
|
|
if (pulled_task || this_rq->nr_running > 0)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
raw_spin_lock(&this_rq->lock);
|
|
|
|
if (curr_cost > this_rq->max_idle_balance_cost)
|
|
this_rq->max_idle_balance_cost = curr_cost;
|
|
|
|
out:
|
|
/*
|
|
* While browsing the domains, we released the rq lock, a task could
|
|
* have been enqueued in the meantime. Since we're not going idle,
|
|
* pretend we pulled a task.
|
|
*/
|
|
if (this_rq->cfs.h_nr_running && !pulled_task)
|
|
pulled_task = 1;
|
|
|
|
/* Move the next balance forward */
|
|
if (time_after(this_rq->next_balance, next_balance))
|
|
this_rq->next_balance = next_balance;
|
|
|
|
/* Is there a task of a high priority class? */
|
|
if (this_rq->nr_running != this_rq->cfs.h_nr_running)
|
|
pulled_task = -1;
|
|
|
|
if (pulled_task)
|
|
this_rq->idle_stamp = 0;
|
|
|
|
rq_repin_lock(this_rq, rf);
|
|
|
|
return pulled_task;
|
|
}
|
|
|
|
/*
|
|
* run_rebalance_domains is triggered when needed from the scheduler tick.
|
|
* Also triggered for nohz idle balancing (with nohz_balancing_kick set).
|
|
*/
|
|
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
|
|
{
|
|
struct rq *this_rq = this_rq();
|
|
enum cpu_idle_type idle = this_rq->idle_balance ?
|
|
CPU_IDLE : CPU_NOT_IDLE;
|
|
|
|
/*
|
|
* If this CPU has a pending nohz_balance_kick, then do the
|
|
* balancing on behalf of the other idle CPUs whose ticks are
|
|
* stopped. Do nohz_idle_balance *before* rebalance_domains to
|
|
* give the idle CPUs a chance to load balance. Else we may
|
|
* load balance only within the local sched_domain hierarchy
|
|
* and abort nohz_idle_balance altogether if we pull some load.
|
|
*/
|
|
if (nohz_idle_balance(this_rq, idle))
|
|
return;
|
|
|
|
/* normal load balance */
|
|
update_blocked_averages(this_rq->cpu);
|
|
rebalance_domains(this_rq, idle);
|
|
}
|
|
|
|
/*
|
|
* Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
|
|
*/
|
|
void trigger_load_balance(struct rq *rq)
|
|
{
|
|
/* Don't need to rebalance while attached to NULL domain */
|
|
if (unlikely(on_null_domain(rq)))
|
|
return;
|
|
|
|
if (time_after_eq(jiffies, rq->next_balance))
|
|
raise_softirq(SCHED_SOFTIRQ);
|
|
|
|
nohz_balancer_kick(rq);
|
|
}
|
|
|
|
static void rq_online_fair(struct rq *rq)
|
|
{
|
|
update_sysctl();
|
|
|
|
update_runtime_enabled(rq);
|
|
}
|
|
|
|
static void rq_offline_fair(struct rq *rq)
|
|
{
|
|
update_sysctl();
|
|
|
|
/* Ensure any throttled groups are reachable by pick_next_task */
|
|
unthrottle_offline_cfs_rqs(rq);
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* scheduler tick hitting a task of our scheduling class.
|
|
*
|
|
* NOTE: This function can be called remotely by the tick offload that
|
|
* goes along full dynticks. Therefore no local assumption can be made
|
|
* and everything must be accessed through the @rq and @curr passed in
|
|
* parameters.
|
|
*/
|
|
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &curr->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
entity_tick(cfs_rq, se, queued);
|
|
}
|
|
|
|
if (static_branch_unlikely(&sched_numa_balancing))
|
|
task_tick_numa(rq, curr);
|
|
|
|
update_misfit_status(curr, rq);
|
|
update_overutilized_status(task_rq(curr));
|
|
}
|
|
|
|
/*
|
|
* called on fork with the child task as argument from the parent's context
|
|
* - child not yet on the tasklist
|
|
* - preemption disabled
|
|
*/
|
|
static void task_fork_fair(struct task_struct *p)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se, *curr;
|
|
struct rq *rq = this_rq();
|
|
struct rq_flags rf;
|
|
|
|
rq_lock(rq, &rf);
|
|
update_rq_clock(rq);
|
|
|
|
cfs_rq = task_cfs_rq(current);
|
|
curr = cfs_rq->curr;
|
|
if (curr) {
|
|
update_curr(cfs_rq);
|
|
se->vruntime = curr->vruntime;
|
|
}
|
|
place_entity(cfs_rq, se, 1);
|
|
|
|
if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
|
|
/*
|
|
* Upon rescheduling, sched_class::put_prev_task() will place
|
|
* 'current' within the tree based on its new key value.
|
|
*/
|
|
swap(curr->vruntime, se->vruntime);
|
|
resched_curr(rq);
|
|
}
|
|
|
|
se->vruntime -= cfs_rq->min_vruntime;
|
|
rq_unlock(rq, &rf);
|
|
}
|
|
|
|
/*
|
|
* Priority of the task has changed. Check to see if we preempt
|
|
* the current task.
|
|
*/
|
|
static void
|
|
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
|
|
{
|
|
if (!task_on_rq_queued(p))
|
|
return;
|
|
|
|
/*
|
|
* Reschedule if we are currently running on this runqueue and
|
|
* our priority decreased, or if we are not currently running on
|
|
* this runqueue and our priority is higher than the current's
|
|
*/
|
|
if (rq->curr == p) {
|
|
if (p->prio > oldprio)
|
|
resched_curr(rq);
|
|
} else
|
|
check_preempt_curr(rq, p, 0);
|
|
}
|
|
|
|
static inline bool vruntime_normalized(struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
|
|
/*
|
|
* In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
|
|
* the dequeue_entity(.flags=0) will already have normalized the
|
|
* vruntime.
|
|
*/
|
|
if (p->on_rq)
|
|
return true;
|
|
|
|
/*
|
|
* When !on_rq, vruntime of the task has usually NOT been normalized.
|
|
* But there are some cases where it has already been normalized:
|
|
*
|
|
* - A forked child which is waiting for being woken up by
|
|
* wake_up_new_task().
|
|
* - A task which has been woken up by try_to_wake_up() and
|
|
* waiting for actually being woken up by sched_ttwu_pending().
|
|
*/
|
|
if (!se->sum_exec_runtime ||
|
|
(p->state == TASK_WAKING && p->sched_remote_wakeup))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
/*
|
|
* Propagate the changes of the sched_entity across the tg tree to make it
|
|
* visible to the root
|
|
*/
|
|
static void propagate_entity_cfs_rq(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
/* Start to propagate at parent */
|
|
se = se->parent;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
|
|
if (cfs_rq_throttled(cfs_rq))
|
|
break;
|
|
|
|
update_load_avg(cfs_rq, se, UPDATE_TG);
|
|
}
|
|
}
|
|
#else
|
|
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
|
|
#endif
|
|
|
|
static void detach_entity_cfs_rq(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
/* Catch up with the cfs_rq and remove our load when we leave */
|
|
update_load_avg(cfs_rq, se, 0);
|
|
detach_entity_load_avg(cfs_rq, se);
|
|
update_tg_load_avg(cfs_rq, false);
|
|
propagate_entity_cfs_rq(se);
|
|
}
|
|
|
|
static void attach_entity_cfs_rq(struct sched_entity *se)
|
|
{
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
/*
|
|
* Since the real-depth could have been changed (only FAIR
|
|
* class maintain depth value), reset depth properly.
|
|
*/
|
|
se->depth = se->parent ? se->parent->depth + 1 : 0;
|
|
#endif
|
|
|
|
/* Synchronize entity with its cfs_rq */
|
|
update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
|
|
attach_entity_load_avg(cfs_rq, se, 0);
|
|
update_tg_load_avg(cfs_rq, false);
|
|
propagate_entity_cfs_rq(se);
|
|
}
|
|
|
|
static void detach_task_cfs_rq(struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
if (!vruntime_normalized(p)) {
|
|
/*
|
|
* Fix up our vruntime so that the current sleep doesn't
|
|
* cause 'unlimited' sleep bonus.
|
|
*/
|
|
place_entity(cfs_rq, se, 0);
|
|
se->vruntime -= cfs_rq->min_vruntime;
|
|
}
|
|
|
|
detach_entity_cfs_rq(se);
|
|
}
|
|
|
|
static void attach_task_cfs_rq(struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
attach_entity_cfs_rq(se);
|
|
|
|
if (!vruntime_normalized(p))
|
|
se->vruntime += cfs_rq->min_vruntime;
|
|
}
|
|
|
|
static void switched_from_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
detach_task_cfs_rq(p);
|
|
}
|
|
|
|
static void switched_to_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
attach_task_cfs_rq(p);
|
|
|
|
if (task_on_rq_queued(p)) {
|
|
/*
|
|
* We were most likely switched from sched_rt, so
|
|
* kick off the schedule if running, otherwise just see
|
|
* if we can still preempt the current task.
|
|
*/
|
|
if (rq->curr == p)
|
|
resched_curr(rq);
|
|
else
|
|
check_preempt_curr(rq, p, 0);
|
|
}
|
|
}
|
|
|
|
/* Account for a task changing its policy or group.
|
|
*
|
|
* This routine is mostly called to set cfs_rq->curr field when a task
|
|
* migrates between groups/classes.
|
|
*/
|
|
static void set_curr_task_fair(struct rq *rq)
|
|
{
|
|
struct sched_entity *se = &rq->curr->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
set_next_entity(cfs_rq, se);
|
|
/* ensure bandwidth has been allocated on our new cfs_rq */
|
|
account_cfs_rq_runtime(cfs_rq, 0);
|
|
}
|
|
}
|
|
|
|
void init_cfs_rq(struct cfs_rq *cfs_rq)
|
|
{
|
|
cfs_rq->tasks_timeline = RB_ROOT_CACHED;
|
|
cfs_rq->min_vruntime = (u64)(-(1LL << 20));
|
|
#ifndef CONFIG_64BIT
|
|
cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
|
|
#endif
|
|
#ifdef CONFIG_SMP
|
|
raw_spin_lock_init(&cfs_rq->removed.lock);
|
|
#endif
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
static void task_set_group_fair(struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
|
|
set_task_rq(p, task_cpu(p));
|
|
se->depth = se->parent ? se->parent->depth + 1 : 0;
|
|
}
|
|
|
|
static void task_move_group_fair(struct task_struct *p)
|
|
{
|
|
detach_task_cfs_rq(p);
|
|
set_task_rq(p, task_cpu(p));
|
|
|
|
#ifdef CONFIG_SMP
|
|
/* Tell se's cfs_rq has been changed -- migrated */
|
|
p->se.avg.last_update_time = 0;
|
|
#endif
|
|
attach_task_cfs_rq(p);
|
|
}
|
|
|
|
static void task_change_group_fair(struct task_struct *p, int type)
|
|
{
|
|
switch (type) {
|
|
case TASK_SET_GROUP:
|
|
task_set_group_fair(p);
|
|
break;
|
|
|
|
case TASK_MOVE_GROUP:
|
|
task_move_group_fair(p);
|
|
break;
|
|
}
|
|
}
|
|
|
|
void free_fair_sched_group(struct task_group *tg)
|
|
{
|
|
int i;
|
|
|
|
destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
|
|
|
|
for_each_possible_cpu(i) {
|
|
if (tg->cfs_rq)
|
|
kfree(tg->cfs_rq[i]);
|
|
if (tg->se)
|
|
kfree(tg->se[i]);
|
|
}
|
|
|
|
kfree(tg->cfs_rq);
|
|
kfree(tg->se);
|
|
}
|
|
|
|
int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
|
|
{
|
|
struct sched_entity *se;
|
|
struct cfs_rq *cfs_rq;
|
|
int i;
|
|
|
|
tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
|
|
if (!tg->cfs_rq)
|
|
goto err;
|
|
tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
|
|
if (!tg->se)
|
|
goto err;
|
|
|
|
tg->shares = NICE_0_LOAD;
|
|
|
|
init_cfs_bandwidth(tg_cfs_bandwidth(tg));
|
|
|
|
for_each_possible_cpu(i) {
|
|
cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
|
|
GFP_KERNEL, cpu_to_node(i));
|
|
if (!cfs_rq)
|
|
goto err;
|
|
|
|
se = kzalloc_node(sizeof(struct sched_entity),
|
|
GFP_KERNEL, cpu_to_node(i));
|
|
if (!se)
|
|
goto err_free_rq;
|
|
|
|
init_cfs_rq(cfs_rq);
|
|
init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
|
|
init_entity_runnable_average(se);
|
|
}
|
|
|
|
return 1;
|
|
|
|
err_free_rq:
|
|
kfree(cfs_rq);
|
|
err:
|
|
return 0;
|
|
}
|
|
|
|
void online_fair_sched_group(struct task_group *tg)
|
|
{
|
|
struct sched_entity *se;
|
|
struct rq *rq;
|
|
int i;
|
|
|
|
for_each_possible_cpu(i) {
|
|
rq = cpu_rq(i);
|
|
se = tg->se[i];
|
|
|
|
raw_spin_lock_irq(&rq->lock);
|
|
update_rq_clock(rq);
|
|
attach_entity_cfs_rq(se);
|
|
sync_throttle(tg, i);
|
|
raw_spin_unlock_irq(&rq->lock);
|
|
}
|
|
}
|
|
|
|
void unregister_fair_sched_group(struct task_group *tg)
|
|
{
|
|
unsigned long flags;
|
|
struct rq *rq;
|
|
int cpu;
|
|
|
|
for_each_possible_cpu(cpu) {
|
|
if (tg->se[cpu])
|
|
remove_entity_load_avg(tg->se[cpu]);
|
|
|
|
/*
|
|
* Only empty task groups can be destroyed; so we can speculatively
|
|
* check on_list without danger of it being re-added.
|
|
*/
|
|
if (!tg->cfs_rq[cpu]->on_list)
|
|
continue;
|
|
|
|
rq = cpu_rq(cpu);
|
|
|
|
raw_spin_lock_irqsave(&rq->lock, flags);
|
|
list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
|
|
raw_spin_unlock_irqrestore(&rq->lock, flags);
|
|
}
|
|
}
|
|
|
|
void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
|
|
struct sched_entity *se, int cpu,
|
|
struct sched_entity *parent)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
|
|
cfs_rq->tg = tg;
|
|
cfs_rq->rq = rq;
|
|
init_cfs_rq_runtime(cfs_rq);
|
|
|
|
tg->cfs_rq[cpu] = cfs_rq;
|
|
tg->se[cpu] = se;
|
|
|
|
/* se could be NULL for root_task_group */
|
|
if (!se)
|
|
return;
|
|
|
|
if (!parent) {
|
|
se->cfs_rq = &rq->cfs;
|
|
se->depth = 0;
|
|
} else {
|
|
se->cfs_rq = parent->my_q;
|
|
se->depth = parent->depth + 1;
|
|
}
|
|
|
|
se->my_q = cfs_rq;
|
|
/* guarantee group entities always have weight */
|
|
update_load_set(&se->load, NICE_0_LOAD);
|
|
se->parent = parent;
|
|
}
|
|
|
|
static DEFINE_MUTEX(shares_mutex);
|
|
|
|
int sched_group_set_shares(struct task_group *tg, unsigned long shares)
|
|
{
|
|
int i;
|
|
|
|
/*
|
|
* We can't change the weight of the root cgroup.
|
|
*/
|
|
if (!tg->se[0])
|
|
return -EINVAL;
|
|
|
|
shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
|
|
|
|
mutex_lock(&shares_mutex);
|
|
if (tg->shares == shares)
|
|
goto done;
|
|
|
|
tg->shares = shares;
|
|
for_each_possible_cpu(i) {
|
|
struct rq *rq = cpu_rq(i);
|
|
struct sched_entity *se = tg->se[i];
|
|
struct rq_flags rf;
|
|
|
|
/* Propagate contribution to hierarchy */
|
|
rq_lock_irqsave(rq, &rf);
|
|
update_rq_clock(rq);
|
|
for_each_sched_entity(se) {
|
|
update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
|
|
update_cfs_group(se);
|
|
}
|
|
rq_unlock_irqrestore(rq, &rf);
|
|
}
|
|
|
|
done:
|
|
mutex_unlock(&shares_mutex);
|
|
return 0;
|
|
}
|
|
#else /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
void free_fair_sched_group(struct task_group *tg) { }
|
|
|
|
int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
|
|
{
|
|
return 1;
|
|
}
|
|
|
|
void online_fair_sched_group(struct task_group *tg) { }
|
|
|
|
void unregister_fair_sched_group(struct task_group *tg) { }
|
|
|
|
#endif /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
|
|
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
|
|
{
|
|
struct sched_entity *se = &task->se;
|
|
unsigned int rr_interval = 0;
|
|
|
|
/*
|
|
* Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
|
|
* idle runqueue:
|
|
*/
|
|
if (rq->cfs.load.weight)
|
|
rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
|
|
|
|
return rr_interval;
|
|
}
|
|
|
|
/*
|
|
* All the scheduling class methods:
|
|
*/
|
|
const struct sched_class fair_sched_class = {
|
|
.next = &idle_sched_class,
|
|
.enqueue_task = enqueue_task_fair,
|
|
.dequeue_task = dequeue_task_fair,
|
|
.yield_task = yield_task_fair,
|
|
.yield_to_task = yield_to_task_fair,
|
|
|
|
.check_preempt_curr = check_preempt_wakeup,
|
|
|
|
.pick_next_task = pick_next_task_fair,
|
|
.put_prev_task = put_prev_task_fair,
|
|
|
|
#ifdef CONFIG_SMP
|
|
.select_task_rq = select_task_rq_fair,
|
|
.migrate_task_rq = migrate_task_rq_fair,
|
|
|
|
.rq_online = rq_online_fair,
|
|
.rq_offline = rq_offline_fair,
|
|
|
|
.task_dead = task_dead_fair,
|
|
.set_cpus_allowed = set_cpus_allowed_common,
|
|
#endif
|
|
|
|
.set_curr_task = set_curr_task_fair,
|
|
.task_tick = task_tick_fair,
|
|
.task_fork = task_fork_fair,
|
|
|
|
.prio_changed = prio_changed_fair,
|
|
.switched_from = switched_from_fair,
|
|
.switched_to = switched_to_fair,
|
|
|
|
.get_rr_interval = get_rr_interval_fair,
|
|
|
|
.update_curr = update_curr_fair,
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
.task_change_group = task_change_group_fair,
|
|
#endif
|
|
};
|
|
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
void print_cfs_stats(struct seq_file *m, int cpu)
|
|
{
|
|
struct cfs_rq *cfs_rq, *pos;
|
|
|
|
rcu_read_lock();
|
|
for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
|
|
print_cfs_rq(m, cpu, cfs_rq);
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
void show_numa_stats(struct task_struct *p, struct seq_file *m)
|
|
{
|
|
int node;
|
|
unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
|
|
|
|
for_each_online_node(node) {
|
|
if (p->numa_faults) {
|
|
tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
|
|
tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
|
|
}
|
|
if (p->numa_group) {
|
|
gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
|
|
gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
|
|
}
|
|
print_numa_stats(m, node, tsf, tpf, gsf, gpf);
|
|
}
|
|
}
|
|
#endif /* CONFIG_NUMA_BALANCING */
|
|
#endif /* CONFIG_SCHED_DEBUG */
|
|
|
|
__init void init_sched_fair_class(void)
|
|
{
|
|
#ifdef CONFIG_SMP
|
|
open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
|
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
nohz.next_balance = jiffies;
|
|
nohz.next_blocked = jiffies;
|
|
zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
|
|
#endif
|
|
#endif /* SMP */
|
|
|
|
}
|