linux-kernel - [PATCH] sched/cpuacct: fix percpu time accounting

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Date:   Wed,  8 Dec 2021 15:38:36 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     mingo@...hat.com, peterz@...radead.org
Cc:     juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>,
        Xuan Lu <luxuan.windniw@...edance.com>,
        Minye Zhu <zhuminye@...edance.com>,
        Qiang Wang <wangqiang.wq.frank@...edance.com>
Subject: [PATCH] sched/cpuacct: fix percpu time accounting

The usage percpu data is the CPU time consumed on each CPU by all tasks
in this cgroup (including tasks lower in the hierarchy). When cpuacct_charge
called from other CPUs, we should use the CPU of task, not this CPU.

e.g.
    cpuacct_charge+1
    update_curr+332
    enqueue_entity+70
    enqueue_task_fair+169
    activate_task+57
    attach_task+46
    load_balance+1512
    run_rebalance_domains+451
    __do_softirq+282
    sysvec_apic_timer_interrupt+159
    asm_sysvec_apic_timer_interrupt+18
    native_safe_halt+11
    default_idle+10
    default_enter_idle+45
    cpuidle_enter_state+130
    cpuidle_enter+47
    do_idle+489
    cpu_startup_entry+25
    start_secondary+261
    secondary_startup_64_no_verify+176

Reported-by: Xuan Lu <luxuan.windniw@...edance.com>
Reported-by: Minye Zhu <zhuminye@...edance.com>
Co-developed-by: Qiang Wang <wangqiang.wq.frank@...edance.com>
Signed-off-by: Qiang Wang <wangqiang.wq.frank@...edance.com>
Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 kernel/sched/cpuacct.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index 893eece65bfd..aab51c88bd34 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -341,6 +341,7 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime)
 	struct cpuacct *ca;
 	int index = CPUACCT_STAT_SYSTEM;
 	struct pt_regs *regs = get_irq_regs() ? : task_pt_regs(tsk);
+	unsigned int cpu = task_cpu(tsk);
 
 	if (regs && user_mode(regs))
 		index = CPUACCT_STAT_USER;
@@ -348,7 +349,7 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime)
 	rcu_read_lock();
 
 	for (ca = task_ca(tsk); ca; ca = parent_ca(ca))
-		__this_cpu_add(ca->cpuusage->usages[index], cputime);
+		per_cpu_ptr(ca->cpuusage, cpu)->usages[index] += cputime;
 
 	rcu_read_unlock();
 }
-- 
2.11.0