linux/kernel/cgroup/rstat.c
Chen Ridong b824766504 cgroup/rstat: add force idle show helper
In the function cgroup_base_stat_cputime_show, there are five
instances of #ifdef, which makes the code not concise.
To address this, add the function cgroup_force_idle_show
to make the code more succinct.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2024-07-05 08:32:08 -10:00

656 lines
18 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#include "cgroup-internal.h"
#include <linux/sched/cputime.h>
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/btf_ids.h>
#include <trace/events/cgroup.h>
static DEFINE_SPINLOCK(cgroup_rstat_lock);
static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock);
static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu);
static struct cgroup_rstat_cpu *cgroup_rstat_cpu(struct cgroup *cgrp, int cpu)
{
return per_cpu_ptr(cgrp->rstat_cpu, cpu);
}
/*
* Helper functions for rstat per CPU lock (cgroup_rstat_cpu_lock).
*
* This makes it easier to diagnose locking issues and contention in
* production environments. The parameter @fast_path determine the
* tracepoints being added, allowing us to diagnose "flush" related
* operations without handling high-frequency fast-path "update" events.
*/
static __always_inline
unsigned long _cgroup_rstat_cpu_lock(raw_spinlock_t *cpu_lock, int cpu,
struct cgroup *cgrp, const bool fast_path)
{
unsigned long flags;
bool contended;
/*
* The _irqsave() is needed because cgroup_rstat_lock is
* spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring
* this lock with the _irq() suffix only disables interrupts on
* a non-PREEMPT_RT kernel. The raw_spinlock_t below disables
* interrupts on both configurations. The _irqsave() ensures
* that interrupts are always disabled and later restored.
*/
contended = !raw_spin_trylock_irqsave(cpu_lock, flags);
if (contended) {
if (fast_path)
trace_cgroup_rstat_cpu_lock_contended_fastpath(cgrp, cpu, contended);
else
trace_cgroup_rstat_cpu_lock_contended(cgrp, cpu, contended);
raw_spin_lock_irqsave(cpu_lock, flags);
}
if (fast_path)
trace_cgroup_rstat_cpu_locked_fastpath(cgrp, cpu, contended);
else
trace_cgroup_rstat_cpu_locked(cgrp, cpu, contended);
return flags;
}
static __always_inline
void _cgroup_rstat_cpu_unlock(raw_spinlock_t *cpu_lock, int cpu,
struct cgroup *cgrp, unsigned long flags,
const bool fast_path)
{
if (fast_path)
trace_cgroup_rstat_cpu_unlock_fastpath(cgrp, cpu, false);
else
trace_cgroup_rstat_cpu_unlock(cgrp, cpu, false);
raw_spin_unlock_irqrestore(cpu_lock, flags);
}
/**
* cgroup_rstat_updated - keep track of updated rstat_cpu
* @cgrp: target cgroup
* @cpu: cpu on which rstat_cpu was updated
*
* @cgrp's rstat_cpu on @cpu was updated. Put it on the parent's matching
* rstat_cpu->updated_children list. See the comment on top of
* cgroup_rstat_cpu definition for details.
*/
__bpf_kfunc void cgroup_rstat_updated(struct cgroup *cgrp, int cpu)
{
raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);
unsigned long flags;
/*
* Speculative already-on-list test. This may race leading to
* temporary inaccuracies, which is fine.
*
* Because @parent's updated_children is terminated with @parent
* instead of NULL, we can tell whether @cgrp is on the list by
* testing the next pointer for NULL.
*/
if (data_race(cgroup_rstat_cpu(cgrp, cpu)->updated_next))
return;
flags = _cgroup_rstat_cpu_lock(cpu_lock, cpu, cgrp, true);
/* put @cgrp and all ancestors on the corresponding updated lists */
while (true) {
struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
struct cgroup *parent = cgroup_parent(cgrp);
struct cgroup_rstat_cpu *prstatc;
/*
* Both additions and removals are bottom-up. If a cgroup
* is already in the tree, all ancestors are.
*/
if (rstatc->updated_next)
break;
/* Root has no parent to link it to, but mark it busy */
if (!parent) {
rstatc->updated_next = cgrp;
break;
}
prstatc = cgroup_rstat_cpu(parent, cpu);
rstatc->updated_next = prstatc->updated_children;
prstatc->updated_children = cgrp;
cgrp = parent;
}
_cgroup_rstat_cpu_unlock(cpu_lock, cpu, cgrp, flags, true);
}
/**
* cgroup_rstat_push_children - push children cgroups into the given list
* @head: current head of the list (= subtree root)
* @child: first child of the root
* @cpu: target cpu
* Return: A new singly linked list of cgroups to be flush
*
* Iteratively traverse down the cgroup_rstat_cpu updated tree level by
* level and push all the parents first before their next level children
* into a singly linked list built from the tail backward like "pushing"
* cgroups into a stack. The root is pushed by the caller.
*/
static struct cgroup *cgroup_rstat_push_children(struct cgroup *head,
struct cgroup *child, int cpu)
{
struct cgroup *chead = child; /* Head of child cgroup level */
struct cgroup *ghead = NULL; /* Head of grandchild cgroup level */
struct cgroup *parent, *grandchild;
struct cgroup_rstat_cpu *crstatc;
child->rstat_flush_next = NULL;
next_level:
while (chead) {
child = chead;
chead = child->rstat_flush_next;
parent = cgroup_parent(child);
/* updated_next is parent cgroup terminated */
while (child != parent) {
child->rstat_flush_next = head;
head = child;
crstatc = cgroup_rstat_cpu(child, cpu);
grandchild = crstatc->updated_children;
if (grandchild != child) {
/* Push the grand child to the next level */
crstatc->updated_children = child;
grandchild->rstat_flush_next = ghead;
ghead = grandchild;
}
child = crstatc->updated_next;
crstatc->updated_next = NULL;
}
}
if (ghead) {
chead = ghead;
ghead = NULL;
goto next_level;
}
return head;
}
/**
* cgroup_rstat_updated_list - return a list of updated cgroups to be flushed
* @root: root of the cgroup subtree to traverse
* @cpu: target cpu
* Return: A singly linked list of cgroups to be flushed
*
* Walks the updated rstat_cpu tree on @cpu from @root. During traversal,
* each returned cgroup is unlinked from the updated tree.
*
* The only ordering guarantee is that, for a parent and a child pair
* covered by a given traversal, the child is before its parent in
* the list.
*
* Note that updated_children is self terminated and points to a list of
* child cgroups if not empty. Whereas updated_next is like a sibling link
* within the children list and terminated by the parent cgroup. An exception
* here is the cgroup root whose updated_next can be self terminated.
*/
static struct cgroup *cgroup_rstat_updated_list(struct cgroup *root, int cpu)
{
raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);
struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(root, cpu);
struct cgroup *head = NULL, *parent, *child;
unsigned long flags;
flags = _cgroup_rstat_cpu_lock(cpu_lock, cpu, root, false);
/* Return NULL if this subtree is not on-list */
if (!rstatc->updated_next)
goto unlock_ret;
/*
* Unlink @root from its parent. As the updated_children list is
* singly linked, we have to walk it to find the removal point.
*/
parent = cgroup_parent(root);
if (parent) {
struct cgroup_rstat_cpu *prstatc;
struct cgroup **nextp;
prstatc = cgroup_rstat_cpu(parent, cpu);
nextp = &prstatc->updated_children;
while (*nextp != root) {
struct cgroup_rstat_cpu *nrstatc;
nrstatc = cgroup_rstat_cpu(*nextp, cpu);
WARN_ON_ONCE(*nextp == parent);
nextp = &nrstatc->updated_next;
}
*nextp = rstatc->updated_next;
}
rstatc->updated_next = NULL;
/* Push @root to the list first before pushing the children */
head = root;
root->rstat_flush_next = NULL;
child = rstatc->updated_children;
rstatc->updated_children = root;
if (child != root)
head = cgroup_rstat_push_children(head, child, cpu);
unlock_ret:
_cgroup_rstat_cpu_unlock(cpu_lock, cpu, root, flags, false);
return head;
}
/*
* A hook for bpf stat collectors to attach to and flush their stats.
* Together with providing bpf kfuncs for cgroup_rstat_updated() and
* cgroup_rstat_flush(), this enables a complete workflow where bpf progs that
* collect cgroup stats can integrate with rstat for efficient flushing.
*
* A static noinline declaration here could cause the compiler to optimize away
* the function. A global noinline declaration will keep the definition, but may
* optimize away the callsite. Therefore, __weak is needed to ensure that the
* call is still emitted, by telling the compiler that we don't know what the
* function might eventually be.
*/
__bpf_hook_start();
__weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
struct cgroup *parent, int cpu)
{
}
__bpf_hook_end();
/*
* Helper functions for locking cgroup_rstat_lock.
*
* This makes it easier to diagnose locking issues and contention in
* production environments. The parameter @cpu_in_loop indicate lock
* was released and re-taken when collection data from the CPUs. The
* value -1 is used when obtaining the main lock else this is the CPU
* number processed last.
*/
static inline void __cgroup_rstat_lock(struct cgroup *cgrp, int cpu_in_loop)
__acquires(&cgroup_rstat_lock)
{
bool contended;
contended = !spin_trylock_irq(&cgroup_rstat_lock);
if (contended) {
trace_cgroup_rstat_lock_contended(cgrp, cpu_in_loop, contended);
spin_lock_irq(&cgroup_rstat_lock);
}
trace_cgroup_rstat_locked(cgrp, cpu_in_loop, contended);
}
static inline void __cgroup_rstat_unlock(struct cgroup *cgrp, int cpu_in_loop)
__releases(&cgroup_rstat_lock)
{
trace_cgroup_rstat_unlock(cgrp, cpu_in_loop, false);
spin_unlock_irq(&cgroup_rstat_lock);
}
/* see cgroup_rstat_flush() */
static void cgroup_rstat_flush_locked(struct cgroup *cgrp)
__releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock)
{
int cpu;
lockdep_assert_held(&cgroup_rstat_lock);
for_each_possible_cpu(cpu) {
struct cgroup *pos = cgroup_rstat_updated_list(cgrp, cpu);
for (; pos; pos = pos->rstat_flush_next) {
struct cgroup_subsys_state *css;
cgroup_base_stat_flush(pos, cpu);
bpf_rstat_flush(pos, cgroup_parent(pos), cpu);
rcu_read_lock();
list_for_each_entry_rcu(css, &pos->rstat_css_list,
rstat_css_node)
css->ss->css_rstat_flush(css, cpu);
rcu_read_unlock();
}
/* play nice and yield if necessary */
if (need_resched() || spin_needbreak(&cgroup_rstat_lock)) {
__cgroup_rstat_unlock(cgrp, cpu);
if (!cond_resched())
cpu_relax();
__cgroup_rstat_lock(cgrp, cpu);
}
}
}
/**
* cgroup_rstat_flush - flush stats in @cgrp's subtree
* @cgrp: target cgroup
*
* Collect all per-cpu stats in @cgrp's subtree into the global counters
* and propagate them upwards. After this function returns, all cgroups in
* the subtree have up-to-date ->stat.
*
* This also gets all cgroups in the subtree including @cgrp off the
* ->updated_children lists.
*
* This function may block.
*/
__bpf_kfunc void cgroup_rstat_flush(struct cgroup *cgrp)
{
might_sleep();
__cgroup_rstat_lock(cgrp, -1);
cgroup_rstat_flush_locked(cgrp);
__cgroup_rstat_unlock(cgrp, -1);
}
/**
* cgroup_rstat_flush_hold - flush stats in @cgrp's subtree and hold
* @cgrp: target cgroup
*
* Flush stats in @cgrp's subtree and prevent further flushes. Must be
* paired with cgroup_rstat_flush_release().
*
* This function may block.
*/
void cgroup_rstat_flush_hold(struct cgroup *cgrp)
__acquires(&cgroup_rstat_lock)
{
might_sleep();
__cgroup_rstat_lock(cgrp, -1);
cgroup_rstat_flush_locked(cgrp);
}
/**
* cgroup_rstat_flush_release - release cgroup_rstat_flush_hold()
* @cgrp: cgroup used by tracepoint
*/
void cgroup_rstat_flush_release(struct cgroup *cgrp)
__releases(&cgroup_rstat_lock)
{
__cgroup_rstat_unlock(cgrp, -1);
}
int cgroup_rstat_init(struct cgroup *cgrp)
{
int cpu;
/* the root cgrp has rstat_cpu preallocated */
if (!cgrp->rstat_cpu) {
cgrp->rstat_cpu = alloc_percpu(struct cgroup_rstat_cpu);
if (!cgrp->rstat_cpu)
return -ENOMEM;
}
/* ->updated_children list is self terminated */
for_each_possible_cpu(cpu) {
struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
rstatc->updated_children = cgrp;
u64_stats_init(&rstatc->bsync);
}
return 0;
}
void cgroup_rstat_exit(struct cgroup *cgrp)
{
int cpu;
cgroup_rstat_flush(cgrp);
/* sanity check */
for_each_possible_cpu(cpu) {
struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
if (WARN_ON_ONCE(rstatc->updated_children != cgrp) ||
WARN_ON_ONCE(rstatc->updated_next))
return;
}
free_percpu(cgrp->rstat_cpu);
cgrp->rstat_cpu = NULL;
}
void __init cgroup_rstat_boot(void)
{
int cpu;
for_each_possible_cpu(cpu)
raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu));
}
/*
* Functions for cgroup basic resource statistics implemented on top of
* rstat.
*/
static void cgroup_base_stat_add(struct cgroup_base_stat *dst_bstat,
struct cgroup_base_stat *src_bstat)
{
dst_bstat->cputime.utime += src_bstat->cputime.utime;
dst_bstat->cputime.stime += src_bstat->cputime.stime;
dst_bstat->cputime.sum_exec_runtime += src_bstat->cputime.sum_exec_runtime;
#ifdef CONFIG_SCHED_CORE
dst_bstat->forceidle_sum += src_bstat->forceidle_sum;
#endif
}
static void cgroup_base_stat_sub(struct cgroup_base_stat *dst_bstat,
struct cgroup_base_stat *src_bstat)
{
dst_bstat->cputime.utime -= src_bstat->cputime.utime;
dst_bstat->cputime.stime -= src_bstat->cputime.stime;
dst_bstat->cputime.sum_exec_runtime -= src_bstat->cputime.sum_exec_runtime;
#ifdef CONFIG_SCHED_CORE
dst_bstat->forceidle_sum -= src_bstat->forceidle_sum;
#endif
}
static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
{
struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
struct cgroup *parent = cgroup_parent(cgrp);
struct cgroup_rstat_cpu *prstatc;
struct cgroup_base_stat delta;
unsigned seq;
/* Root-level stats are sourced from system-wide CPU stats */
if (!parent)
return;
/* fetch the current per-cpu values */
do {
seq = __u64_stats_fetch_begin(&rstatc->bsync);
delta = rstatc->bstat;
} while (__u64_stats_fetch_retry(&rstatc->bsync, seq));
/* propagate per-cpu delta to cgroup and per-cpu global statistics */
cgroup_base_stat_sub(&delta, &rstatc->last_bstat);
cgroup_base_stat_add(&cgrp->bstat, &delta);
cgroup_base_stat_add(&rstatc->last_bstat, &delta);
cgroup_base_stat_add(&rstatc->subtree_bstat, &delta);
/* propagate cgroup and per-cpu global delta to parent (unless that's root) */
if (cgroup_parent(parent)) {
delta = cgrp->bstat;
cgroup_base_stat_sub(&delta, &cgrp->last_bstat);
cgroup_base_stat_add(&parent->bstat, &delta);
cgroup_base_stat_add(&cgrp->last_bstat, &delta);
delta = rstatc->subtree_bstat;
prstatc = cgroup_rstat_cpu(parent, cpu);
cgroup_base_stat_sub(&delta, &rstatc->last_subtree_bstat);
cgroup_base_stat_add(&prstatc->subtree_bstat, &delta);
cgroup_base_stat_add(&rstatc->last_subtree_bstat, &delta);
}
}
static struct cgroup_rstat_cpu *
cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp, unsigned long *flags)
{
struct cgroup_rstat_cpu *rstatc;
rstatc = get_cpu_ptr(cgrp->rstat_cpu);
*flags = u64_stats_update_begin_irqsave(&rstatc->bsync);
return rstatc;
}
static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp,
struct cgroup_rstat_cpu *rstatc,
unsigned long flags)
{
u64_stats_update_end_irqrestore(&rstatc->bsync, flags);
cgroup_rstat_updated(cgrp, smp_processor_id());
put_cpu_ptr(rstatc);
}
void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec)
{
struct cgroup_rstat_cpu *rstatc;
unsigned long flags;
rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
rstatc->bstat.cputime.sum_exec_runtime += delta_exec;
cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
}
void __cgroup_account_cputime_field(struct cgroup *cgrp,
enum cpu_usage_stat index, u64 delta_exec)
{
struct cgroup_rstat_cpu *rstatc;
unsigned long flags;
rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
switch (index) {
case CPUTIME_USER:
case CPUTIME_NICE:
rstatc->bstat.cputime.utime += delta_exec;
break;
case CPUTIME_SYSTEM:
case CPUTIME_IRQ:
case CPUTIME_SOFTIRQ:
rstatc->bstat.cputime.stime += delta_exec;
break;
#ifdef CONFIG_SCHED_CORE
case CPUTIME_FORCEIDLE:
rstatc->bstat.forceidle_sum += delta_exec;
break;
#endif
default:
break;
}
cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
}
/*
* compute the cputime for the root cgroup by getting the per cpu data
* at a global level, then categorizing the fields in a manner consistent
* with how it is done by __cgroup_account_cputime_field for each bit of
* cpu time attributed to a cgroup.
*/
static void root_cgroup_cputime(struct cgroup_base_stat *bstat)
{
struct task_cputime *cputime = &bstat->cputime;
int i;
memset(bstat, 0, sizeof(*bstat));
for_each_possible_cpu(i) {
struct kernel_cpustat kcpustat;
u64 *cpustat = kcpustat.cpustat;
u64 user = 0;
u64 sys = 0;
kcpustat_cpu_fetch(&kcpustat, i);
user += cpustat[CPUTIME_USER];
user += cpustat[CPUTIME_NICE];
cputime->utime += user;
sys += cpustat[CPUTIME_SYSTEM];
sys += cpustat[CPUTIME_IRQ];
sys += cpustat[CPUTIME_SOFTIRQ];
cputime->stime += sys;
cputime->sum_exec_runtime += user;
cputime->sum_exec_runtime += sys;
cputime->sum_exec_runtime += cpustat[CPUTIME_STEAL];
#ifdef CONFIG_SCHED_CORE
bstat->forceidle_sum += cpustat[CPUTIME_FORCEIDLE];
#endif
}
}
static void cgroup_force_idle_show(struct seq_file *seq, struct cgroup_base_stat *bstat)
{
#ifdef CONFIG_SCHED_CORE
u64 forceidle_time = bstat->forceidle_sum;
do_div(forceidle_time, NSEC_PER_USEC);
seq_printf(seq, "core_sched.force_idle_usec %llu\n", forceidle_time);
#endif
}
void cgroup_base_stat_cputime_show(struct seq_file *seq)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
u64 usage, utime, stime;
if (cgroup_parent(cgrp)) {
cgroup_rstat_flush_hold(cgrp);
usage = cgrp->bstat.cputime.sum_exec_runtime;
cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime,
&utime, &stime);
cgroup_rstat_flush_release(cgrp);
} else {
/* cgrp->bstat of root is not actually used, reuse it */
root_cgroup_cputime(&cgrp->bstat);
usage = cgrp->bstat.cputime.sum_exec_runtime;
utime = cgrp->bstat.cputime.utime;
stime = cgrp->bstat.cputime.stime;
}
do_div(usage, NSEC_PER_USEC);
do_div(utime, NSEC_PER_USEC);
do_div(stime, NSEC_PER_USEC);
seq_printf(seq, "usage_usec %llu\n"
"user_usec %llu\n"
"system_usec %llu\n",
usage, utime, stime);
cgroup_force_idle_show(seq, &cgrp->bstat);
}
/* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */
BTF_KFUNCS_START(bpf_rstat_kfunc_ids)
BTF_ID_FLAGS(func, cgroup_rstat_updated)
BTF_ID_FLAGS(func, cgroup_rstat_flush, KF_SLEEPABLE)
BTF_KFUNCS_END(bpf_rstat_kfunc_ids)
static const struct btf_kfunc_id_set bpf_rstat_kfunc_set = {
.owner = THIS_MODULE,
.set = &bpf_rstat_kfunc_ids,
};
static int __init bpf_rstat_kfunc_init(void)
{
return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,
&bpf_rstat_kfunc_set);
}
late_initcall(bpf_rstat_kfunc_init);