Messages in this thread Patch in this message | | | From | Cruz Zhao <> | Subject | [PATCH] sched/core: fix inaccurate idle stat in /proc/stat when force idle | Date | Mon, 19 Jun 2023 01:02:40 +0800 |
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When force idle, rq->curr == rq->idle but rq->nr_running > 0, results that idle_cpu() returns 0. In function tick_irq_exit(), if idle_cpu() is 0, tick_nohz_irq_exit() will not be called, and ts->idle_active will not become 1, which became 0 in tick_nohz_irq_enter(). ts->idle_sleeptime won't update in function update_ts_time_stats(), if ts->idle_active is 0, which should be 1. And this bug will result that ts->idle_sleeptime is less than the actual value, and finally will result that the idle time in /proc/stat is less than the actual value.
To fix this problem, we introduce sched_core_idle_cpu(), which returns true when force idle, and we change the judgment criteria from idle_cpu() to sched_core_idle_cpu() in function tick_irq_exit().
Signed-off-by: Cruz Zhao <CruzZhao@linux.alibaba.com> --- include/linux/sched.h | 2 ++ kernel/sched/core.c | 13 +++++++++++++ kernel/softirq.c | 2 +- 3 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h index b09a83bfad8b..73e61c0f10a7 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2430,9 +2430,11 @@ extern void sched_core_free(struct task_struct *tsk); extern void sched_core_fork(struct task_struct *p); extern int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type, unsigned long uaddr); +extern int sched_core_idle_cpu(int cpu); #else static inline void sched_core_free(struct task_struct *tsk) { } static inline void sched_core_fork(struct task_struct *p) { } +static inline int sched_core_idle_cpu(int cpu) { return idle_cpu(cpu); } #endif extern void sched_set_stop_task(int cpu, struct task_struct *stop); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 71c1a0f232b4..c80088956987 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7286,6 +7286,19 @@ struct task_struct *idle_task(int cpu) return cpu_rq(cpu)->idle; } +#ifdef CONFIG_SCHED_CORE +int sched_core_idle_cpu(int cpu) +{ + struct rq *rq = cpu_rq(cpu); + + if (sched_core_enabled(rq) && rq->curr == rq->idle) + return 1; + + return idle_cpu(cpu); +} + +#endif + #ifdef CONFIG_SMP /* * This function computes an effective utilization for the given CPU, to be diff --git a/kernel/softirq.c b/kernel/softirq.c index c8a6913c067d..98b98991ce45 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -630,7 +630,7 @@ static inline void tick_irq_exit(void) int cpu = smp_processor_id(); /* Make sure that timer wheel updates are propagated */ - if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { + if ((sched_core_idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { if (!in_hardirq()) tick_nohz_irq_exit(); } -- 2.27.0
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