Messages in this thread Patch in this message | | | Subject | Re: [PATCH 2/4] sched/fair: Do not replace recent_used_cpu with the new target | From | Dietmar Eggemann <> | Date | Tue, 8 Dec 2020 10:57:29 +0100 |
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On 07/12/2020 10:15, Mel Gorman wrote: > After select_idle_sibling, p->recent_used_cpu is set to the > new target. However on the next wakeup, prev will be the same as
I'm confused here. Isn't current->recent_used_cpu set to 'cpu = smp_processor_id()' after sis()? Looking at v5.10-rc6.
[...]
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 23934dbac635..01b38fc17bca 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6274,6 +6274,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) > > /* Check a recently used CPU as a potential idle candidate: */ > recent_used_cpu = p->recent_used_cpu; > + p->recent_used_cpu = prev; > if (recent_used_cpu != prev && > recent_used_cpu != target && > cpus_share_cache(recent_used_cpu, target) &&
p->recent_used_cpu is already set to prev in this if condition.
asym_fits_capacity(task_util, recent_used_cpu)) { /* * Replace recent_used_cpu with prev as it is a potential * candidate for the next wake: */ p->recent_used_cpu = prev; return recent_used_cpu;
> @@ -6765,9 +6766,6 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) > } else if (wake_flags & WF_TTWU) { /* XXX always ? */ > /* Fast path */ > new_cpu = select_idle_sibling(p, prev_cpu, new_cpu); > - > - if (want_affine) > - current->recent_used_cpu = cpu; > } > rcu_read_unlock();
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