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c628db0a68
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Shrikanth Hegde c628db0a68 sched/fair: Check root_domain::overload value before update 
The root_domain::overload flag is 1 when there's any rq
in the root domain that has 2 or more running tasks. (Ie. it's overloaded.)

The root_domain structure itself is a global structure per cpuset island.

The ::overload flag is maintained the following way:

  - Set when adding a second task to the runqueue.

  - It is cleared in update_sd_lb_stats() during load balance,
    if none of the rqs have 2 or more running tasks.

This flag is used during newidle balance to see if its worth doing a full
load balance pass, which can be an expensive operation. If it is set,
then newidle balance will try to aggressively pull a task.

Since commit:

  630246a06a ("sched/fair: Clean-up update_sg_lb_stats parameters")

::overload is being written unconditionally, even if it has the same
value. The change in value of this depends on the workload, but on
typical workloads, it doesn't change all that often: a system is
either dominantly overloaded for substantial amounts of time, or not.

Extra writes to this semi-global structure cause unnecessary overhead, extra
bus traffic, etc. - so avoid it as much as possible.

Perf probe stats show that it's worth making this change (numbers are
with patch applied):

	1M    probe:sched_balance_newidle_L38
	139   probe:update_sd_lb_stats_L53     <====== 1->0 writes
	129K  probe:add_nr_running_L12
	74    probe:add_nr_running_L13         <====== 0->1 writes
	54K   probe:update_sd_lb_stats_L50     <====== reads

These numbers prove that actual change in the ::overload value is (much) less
frequent: L50 is much larger at ~54,000 accesses vs L53+L13 of 139+74.

[ mingo: Rewrote the changelog. ]

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Qais Yousef <qyousef@layalina.io>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20240325054505.201995-2-sshegde@linux.ibm.com
2024-03-28 11:30:13 +01:00
..
bpf bpf: report RCU QS in cpumap kthread 2024-03-20 21:05:43 -07:00
cgroup Networking changes for 6.9. 2024-03-12 17:44:08 -07:00
configs Networking changes for 6.9. 2024-03-12 17:44:08 -07:00
debug kdb: Fix a potential buffer overflow in kdb_local() 2024-01-17 17:19:06 +00:00
dma dma-mapping fixes for Linux 6.9 2024-03-24 10:45:31 -07:00
entry entry: Respect changes to system call number by trace_sys_enter() 2024-03-12 13:23:32 +01:00
events - Sumanth Korikkar has taught s390 to allocate hotplug-time page frames 2024-03-14 17:43:30 -07:00
futex futex: Prevent the reuse of stale pi_state 2024-01-19 12:58:17 +01:00
gcov gcov: annotate struct gcov_iterator with __counted_by 2023-10-18 14:43:22 -07:00
irq Updates for the MSI interrupt subsystem and RISC-V initial MSI support: 2024-03-11 14:03:03 -07:00
kcsan mm: delete checks for xor_unlock_is_negative_byte() 2023-10-18 14:34:17 -07:00
livepatch livepatch: Fix missing newline character in klp_resolve_symbols() 2023-09-20 11:24:18 +02:00
locking locking/rtmutex: Use try_cmpxchg_relaxed() in mark_rt_mutex_waiters() 2024-03-01 13:02:05 +01:00
module Kbuild updates for v6.9 2024-03-21 14:41:00 -07:00
power RTC for 6.9 2024-03-21 17:16:46 -07:00
printk TTY/Serial driver update for 6.9-rc1 2024-03-21 12:44:10 -07:00
rcu Merge branches 'rcu-doc.2024.02.14a', 'rcu-nocb.2024.02.14a', 'rcu-exp.2024.02.14a', 'rcu-tasks.2024.02.26a' and 'rcu-misc.2024.02.14a' into rcu.2024.02.26a 2024-02-26 17:37:25 -08:00
sched sched/fair: Check root_domain::overload value before update 2024-03-28 11:30:13 +01:00
time Linux 6.9-rc1 2024-03-25 11:32:29 +01:00
trace tracing: Use div64_u64() instead of do_div() 2024-03-18 10:33:06 -04:00
.gitignore
acct.c fs: rename __mnt_{want,drop}_write*() helpers 2023-09-11 15:05:50 +02:00
async.c async: Use a dedicated unbound workqueue with raised min_active 2024-02-09 11:13:59 -10:00
audit_fsnotify.c audit: fix potential double free on error path from fsnotify_add_inode_mark 2022-08-22 18:50:06 -04:00
audit_tree.c As usual, lots of singleton and doubleton patches all over the tree and 2023-11-02 20:53:31 -10:00
audit_watch.c audit: don't WARN_ON_ONCE(!current->mm) in audit_exe_compare() 2023-11-14 17:34:27 -05:00
audit.c audit: use KMEM_CACHE() instead of kmem_cache_create() 2024-01-25 10:12:22 -05:00
audit.h audit: correct audit_filter_inodes() definition 2023-07-21 12:17:25 -04:00
auditfilter.c audit: remove unnecessary assignment in audit_dupe_lsm_field() 2024-01-25 09:59:27 -05:00
auditsc.c audit,io_uring: io_uring openat triggers audit reference count underflow 2023-10-13 18:34:46 +02:00
backtracetest.c backtracetest: Convert from tasklet to BH workqueue 2024-02-05 13:22:34 -10:00
bounds.c bounds: support non-power-of-two CONFIG_NR_CPUS 2024-02-22 15:38:51 -08:00
capability.c lsm: constify the 'target' parameter in security_capget() 2023-08-08 16:48:47 -04:00
cfi.c cfi: Switch to -fsanitize=kcfi 2022-09-26 10:13:13 -07:00
compat.c sched_getaffinity: don't assume 'cpumask_size()' is fully initialized 2023-03-14 19:32:38 -07:00
configs.c
context_tracking.c context_tracking: Fix kerneldoc headers for __ct_user_{enter,exit}() 2024-02-14 07:53:50 -08:00
cpu_pm.c cpuidle, cpu_pm: Remove RCU fiddling from cpu_pm_{enter,exit}() 2023-01-13 11:48:15 +01:00
cpu.c Rework of APIC enumeration and topology evaluation: 2024-03-11 15:45:55 -07:00
crash_core.c crash: split crash dumping code out from kexec_core.c 2024-02-23 17:48:22 -08:00
crash_reserve.c kexec: split crashkernel reservation code out from crash_core.c 2024-02-23 17:48:21 -08:00
cred.c cred: Use KMEM_CACHE() instead of kmem_cache_create() 2024-02-23 17:33:31 -05:00
delayacct.c delayacct: track delays from IRQ/SOFTIRQ 2023-04-18 16:39:34 -07:00
dma.c
elfcorehdr.c crash: remove dependency of FA_DUMP on CRASH_DUMP 2024-02-23 17:48:22 -08:00
exec_domain.c
exit.c vfs-6.9.pidfd 2024-03-11 10:21:06 -07:00
exit.h exit: add internal include file with helpers 2023-09-21 12:03:50 -06:00
extable.c
fail_function.c kernel/fail_function: fix memory leak with using debugfs_lookup() 2023-02-08 13:36:22 +01:00
fork.c RCU pull request for v6.9 2024-03-11 12:02:50 -07:00
freezer.c Linux 6.7-rc6 2023-12-23 15:52:13 +01:00
gen_kheaders.sh Revert "kheaders: substituting --sort in archive creation" 2023-05-28 16:20:21 +09:00
groups.c groups: Convert group_info.usage to refcount_t 2023-09-29 11:28:39 -07:00
hung_task.c kernel/hung_task.c: export sysctl_hung_task_timeout_secs 2024-03-13 21:22:04 -04:00
iomem.c kernel/iomem.c: remove __weak ioremap_cache helper 2023-08-21 13:37:28 -07:00
irq_work.c trace: Add trace_ipi_send_cpu() 2023-03-24 11:01:29 +01:00
jump_label.c jump_label: Prevent key->enabled int overflow 2022-12-01 15:53:05 -08:00
kallsyms_internal.h kallsyms: Reduce the memory occupied by kallsyms_seqs_of_names[] 2022-11-12 18:47:36 -08:00
kallsyms_selftest.c mm/vmalloc: remove vmap_area_list 2024-02-23 17:48:19 -08:00
kallsyms_selftest.h kallsyms: Add self-test facility 2022-11-15 00:42:02 -08:00
kallsyms.c kallsyms: Change func signature for cleanup_symbol_name() 2023-08-25 15:00:36 -07:00
kcmp.c file: convert to SLAB_TYPESAFE_BY_RCU 2023-10-19 11:02:48 +02:00
Kconfig.freezer
Kconfig.hz
Kconfig.kexec crash: clean up kdump related config items 2024-02-23 17:48:22 -08:00
Kconfig.locks
Kconfig.preempt
kcov.c kcov: add prototypes for helper functions 2023-06-09 17:44:17 -07:00
kexec_core.c - Kuan-Wei Chiu has developed the well-named series "lib min_heap: Min 2024-03-14 18:03:09 -07:00
kexec_elf.c
kexec_file.c arm64, crash: wrap crash dumping code into crash related ifdefs 2024-02-23 17:48:23 -08:00
kexec_internal.h crash: remove dependency of FA_DUMP on CRASH_DUMP 2024-02-23 17:48:22 -08:00
kexec.c crash: split crash dumping code out from kexec_core.c 2024-02-23 17:48:22 -08:00
kheaders.c kheaders: Use array declaration instead of char 2023-03-24 20:10:59 -07:00
kprobes.c kprobes: Remove unnecessary initial values of variables 2024-02-08 23:29:29 +09:00
ksyms_common.c kallsyms: make kallsyms_show_value() as generic function 2023-06-08 12:27:20 -07:00
ksysfs.c Driver core changes for 6.9-rc1 2024-03-21 13:34:15 -07:00
kthread.c As usual, lots of singleton and doubleton patches all over the tree and 2023-11-02 20:53:31 -10:00
latencytop.c latencytop: use the last element of latency_record of system 2022-09-11 21:55:12 -07:00
Makefile crash: split crash dumping code out from kexec_core.c 2024-02-23 17:48:22 -08:00
module_signature.c
notifier.c notifiers: add tracepoints to the notifiers infrastructure 2023-04-08 13:45:38 -07:00
nsproxy.c pidfd: add pidfs 2024-03-01 12:23:37 +01:00
numa.c kernel/numa.c: Move logging out of numa.h 2023-12-20 19:26:30 -05:00
padata.c Author: Gang Li padata: dispatch works on 2024-03-06 13:04:17 -08:00
panic.c - Kuan-Wei Chiu has developed the well-named series "lib min_heap: Min 2024-03-14 18:03:09 -07:00
params.c params: Fix multi-line comment style 2023-12-01 09:51:44 -08:00
pid_namespace.c wait: Remove uapi header file from main header file 2023-12-20 19:26:31 -05:00
pid_sysctl.h memfd: replace ratcheting feature from vm.memfd_noexec with hierarchy 2023-08-21 13:37:59 -07:00
pid.c pidfs: remove config option 2024-03-13 12:53:53 -07:00
profile.c kernel/profile.c: simplify duplicated code in profile_setup() 2022-09-11 21:55:12 -07:00
ptrace.c ptrace_attach: shift send(SIGSTOP) into ptrace_set_stopped() 2024-02-22 15:38:52 -08:00
range.c
reboot.c Thermal control updates for 6.8-rc1 2024-01-09 16:20:17 -08:00
regset.c
relay.c kernel: relay: remove relay_file_splice_read dead code, doesn't work 2023-12-29 12:22:27 -08:00
resource_kunit.c
resource.c Quite a lot of kexec work this time around. Many singleton patches in 2024-01-09 11:46:20 -08:00
rseq.c rseq: Extend struct rseq with per-memory-map concurrency ID 2022-12-27 12:52:12 +01:00
scftorture.c scftorture: Pause testing after memory-allocation failure 2023-07-14 15:02:57 -07:00
scs.c scs: add support for dynamic shadow call stacks 2022-11-09 18:06:35 +00:00
seccomp.c file: remove __receive_fd() 2023-12-12 14:24:14 +01:00
signal.c - Kuan-Wei Chiu has developed the well-named series "lib min_heap: Min 2024-03-14 18:03:09 -07:00
smp.c CSD lock commits for v6.7 2023-10-30 17:56:53 -10:00
smpboot.c kthread: add kthread_stop_put 2023-10-04 10:41:57 -07:00
smpboot.h
softirq.c workqueue: Drain BH work items on hot-unplugged CPUs 2024-02-29 11:51:24 -10:00
stackleak.c stackleak: allow to specify arch specific stackleak poison function 2023-04-20 11:36:35 +02:00
stacktrace.c stacktrace: fix kernel-doc typo 2023-12-29 12:22:29 -08:00
static_call_inline.c static_call: Add call depth tracking support 2022-10-17 16:41:16 +02:00
static_call.c
stop_machine.c
sys_ni.c lsm/stable-6.8 PR 20240105 2024-01-09 12:57:46 -08:00
sys.c getrusage: use sig->stats_lock rather than lock_task_sighand() 2024-02-07 21:20:32 -08:00
sysctl-test.c kernel/sysctl-test: use SYSCTL_{ZERO/ONE_HUNDRED} instead of i_{zero/one_hundred} 2022-09-08 16:56:45 -07:00
sysctl.c tracing: Support to dump instance traces by ftrace_dump_on_oops 2024-03-18 10:33:06 -04:00
task_work.c task_work: add kerneldoc annotation for 'data' argument 2023-09-19 13:21:32 -07:00
taskstats.c taskstats: fill_stats_for_tgid: use for_each_thread() 2023-10-04 10:41:57 -07:00
torture.c torture: Print out torture module parameters 2023-09-24 17:24:01 +02:00
tracepoint.c tracepoint: Allow livepatch module add trace event 2023-02-18 14:34:36 -05:00
tsacct.c
ucount.c sysctl: Add size to register_sysctl 2023-08-15 15:26:17 -07:00
uid16.c
uid16.h
umh.c sysctl: fix unused proc_cap_handler() function warning 2023-06-29 15:19:43 -07:00
up.c smp: Change function signatures to use call_single_data_t 2023-09-13 14:59:24 +02:00
user_namespace.c user_namespace: remove unnecessary NULL values from kbuf 2024-02-22 15:38:52 -08:00
user-return-notifier.c
user.c binfmt_misc: enable sandboxed mounts 2023-10-11 08:46:01 -07:00
usermode_driver.c
utsname_sysctl.c utsname: simplify one-level sysctl registration for uts_kern_table 2023-04-13 11:49:35 -07:00
utsname.c
vhost_task.c vhost: Fix worker hangs due to missed wake up calls 2023-06-08 15:43:09 -04:00
vmcore_info.c crash_core: export vmemmap when CONFIG_SPARSEMEM_VMEMMAP is enabled 2024-03-04 17:01:27 -08:00
watch_queue.c watch_queue: fix kcalloc() arguments order 2023-12-21 13:17:54 +01:00
watchdog_buddy.c watchdog/hardlockup: move SMP barriers from common code to buddy code 2023-06-19 16:25:28 -07:00
watchdog_perf.c watchdog/perf: add a weak function for an arch to detect if perf can use NMIs 2023-06-09 17:44:21 -07:00
watchdog.c watchdog/core: remove sysctl handlers from public header 2024-03-12 13:09:23 -07:00
workqueue_internal.h workqueue: Drop the special locking rule for worker->flags and worker_pool->flags 2023-08-07 15:57:22 -10:00
workqueue.c Linux 6.9-rc1 2024-03-25 11:32:29 +01:00