Messages in this thread Patch in this message | | | From | Libo Chen <> | Subject | [PATCH 1/1] sched/fair: Fix inaccurate tally of ttwu_move_affine | Date | Wed, 10 Aug 2022 15:33:13 -0700 |
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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); -- 2.31.1
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