Messages in this thread Patch in this message | | | Date | Mon, 18 Jun 2012 22:41:52 +0800 | From | Charles Wang <> | Subject | Re: [PATCH] sched: Folding nohz load accounting more accurate |
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Peter's patch works the well. Now I ported the second patch to fix high load problem based on Peter's. It works fine on my testing environment. Doug, please try this. Thanks.
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
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4101a0e..180e612 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2228,6 +2228,7 @@ void calc_load_account_idle(struct rq *this_rq) int idx;
delta = calc_load_fold_active(this_rq); + this_rq->last_idle_enter = jiffies;
if (delta) { idx = calc_load_write_idx(); atomic_long_add(delta, &calc_load_idle[idx]); @@ -2431,15 +2432,27 @@ void calc_global_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;
+ last_idle_time_elapse = this_rq->last_idle_enter - calc_load_update; + 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_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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