The following commit has been merged into the sched/core branch of tip: Commit-ID: 39afe5d6fc59237ff7738bf3ede5a8856822d59d Gitweb: https://git.kernel.org/tip/39afe5d6fc59237ff7738bf3ede5a8856822d59d Author: Libo Chen <libo.chen@xxxxxxxxxx> AuthorDate: Wed, 10 Aug 2022 15:33:13 -07:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Wed, 05 Apr 2023 09:58:48 +02:00 sched/fair: Fix inaccurate tally of ttwu_move_affine 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@xxxxxxxxxx> Signed-off-by: Libo Chen <libo.chen@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx> Link: https://lore.kernel.org/r/20220810223313.386614-1-libo.chen@xxxxxxxxxx --- 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 bc358dc..f5da01a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6582,7 +6582,7 @@ 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);
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