Messages in this thread Patch in this message | | | From | Charles Wang <> | Subject | [PATCH 2/2] sched: Try fix sampling time line for idle | Date | Mon, 18 Jun 2012 15:12:50 +0800 |
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In our mind per-cpu sampling for cpu idle and non-idle is equal. But actually may not. For non-idle cpu sampling, it's right the load when sampling. But for idle, cause of nohz, the sampling will be delayed to nohz exit(less than 1 tick after nohz exit). Nohz exit is always caused by processes woken up--non-idle model. It's not fair here. Idle sampling will be turned to non-idle sampling. And cause loadavg being higher than normal.
time-expected-sampling | time-do-sampling | | V V -|-------------------------|-- start_nohz stop_nohz
CC: Peter Zijlstra <peterz@infradead.org> CC: Doug Smythies <dsmythies@telus.net> CC: Ingo Molnar <mingo@redhat.com> CC: Tao Ma <tm@tao.ma> CC: Sha Zhengju <handai.szj@gmail.com> Reported-by: Sha Zhengju <handai.szj@gmail.com> Signed-off-by: Charles Wang <muming.wq@taobao.com>
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 691e7ec..2983838 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2166,6 +2166,7 @@ unsigned long this_cpu_load(void) static atomic_long_t calc_load_tasks; static unsigned long calc_load_update; static unsigned long calc_mask_update; +static unsigned long calc_load_time_start = LOAD_FREQ; unsigned long avenrun[3]; EXPORT_SYMBOL(avenrun); @@ -2260,6 +2261,7 @@ void calc_load_account_idle(struct rq *this_rq) long delta; delta = calc_load_fold_active(this_rq); + this_rq->last_idle_enter = jiffies; if (delta) { atomic_long_add(delta, &calc_load_tasks_idle); /* @@ -2499,6 +2501,8 @@ void prepare_calc_load(void) static void calc_load_account_active(struct rq *this_rq) { long delta; + unsigned long delta_time; + long last_idle_time_elapse; if (time_before(jiffies, this_rq->calc_load_update)) return; @@ -2508,15 +2512,24 @@ static void calc_load_account_active(struct rq *this_rq) atomic_long_xchg(&calc_unmask_cpu_load_idle, 0); delta = atomic_long_xchg(&calc_load_tasks_idle, 0); atomic_long_add(delta, &calc_load_tasks); + calc_load_time_start = jiffies; } /* mark this cpu as load calculated */ set_cpu_load_update_mask(); + last_idle_time_elapse = this_rq->last_idle_enter - calc_load_time_start; + delta_time = jiffies - this_rq->calc_load_update; + if (last_idle_time_elapse > 0) + goto out; + if ((last_idle_time_elapse > -1) && (delta_time >= 1)) + goto out; + delta = calc_load_fold_active(this_rq); delta += calc_load_fold_unmask_idle(); if (delta) atomic_long_add(delta, &calc_load_tasks); +out: this_rq->calc_load_update += LOAD_FREQ; } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 4134d37..a356588 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -438,6 +438,7 @@ struct rq { /* calc_load related fields */ unsigned long calc_load_update; + unsigned long last_idle_enter; long calc_load_active; #ifdef CONFIG_SCHED_HRTICK -- 1.7.9.5
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