Messages in this thread | | | From | Libo Chen <> | Subject | Re: [PATCH 1/1] sched/fair: Fix inaccurate tally of ttwu_move_affine | Date | Thu, 9 Mar 2023 03:17:50 +0000 |
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> On Jan 9, 2023, at 2:00 PM, Libo Chen <libo.chen@oracle.com> wrote: > > Hi Peter, > > A gentle ping~ Vincent has signed it off. Let me know what else I should do for this patch. > > Libo > > On 8/15/22 12:19 PM, Libo Chen wrote: >> >> >> On 8/15/22 04:01, Peter Zijlstra wrote: >>> On Wed, Aug 10, 2022 at 03:33:13PM -0700, Libo Chen wrote: >>>> There are scenarios where non-affine wakeups are incorrectly counted as >>>> affine wakeups by schedstats. >>>> >>>> When wake_affine_idle() returns prev_cpu which doesn't equal to >>>> nr_cpumask_bits, it will slip through the check: target == nr_cpumask_bits >>>> in wake_affine() and be counted as if target == this_cpu in schedstats. >>>> >>>> Replace target == nr_cpumask_bits with target != this_cpu to make sure >>>> affine wakeups are accurately tallied. >>>> >>>> Fixes: 806486c377e33 (sched/fair: Do not migrate if the prev_cpu is idle) >>>> Suggested-by: Daniel Jordan <daniel.m.jordan@oracle.com> >>>> Signed-off-by: Libo Chen <libo.chen@oracle.com> >>>> --- >>>> kernel/sched/fair.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>>> index da388657d5ac..b179da4f8105 100644 >>>> --- a/kernel/sched/fair.c >>>> +++ b/kernel/sched/fair.c >>>> @@ -6114,7 +6114,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, >>>> target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync); >>>> schedstat_inc(p->stats.nr_wakeups_affine_attempts); >>>> - if (target == nr_cpumask_bits) >>>> + if (target != this_cpu) >>>> return prev_cpu; >>>> schedstat_inc(sd->ttwu_move_affine); >>> This not only changes the accounting but also the placement, no? >> No, it should only change the accounting. wake_affine() still returns prev_cpu if target equals to prev_cpu or nr_cpumask_bits, the same behavior as before. >>
Hi Peter,
A second ping in case you missed the first one, what else should I do to get this fix in?
Libo
>> >> Libo >
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