From: Vincent Guittot Date: Fri, 10 Apr 2026 13:23:21 +0000 (+0200) Subject: sched/eevdf: Clear buddies for preempt_short X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=78cde54ea5f03398f1cf6656de2472068f6da966;p=thirdparty%2Fkernel%2Flinux.git sched/eevdf: Clear buddies for preempt_short next buddy should not prevent shorter slice preemption. Don't take buddy into account when checking if shorter slice entity can preempt and clear it if the entity with a shorter slice can preempt current. Test on snapdragon rb5: hackbench -T -p -l 16000000 -g 2 1> /dev/null & hackbench runs in cgroup /test-A cyclictest -t 1 -i 2777 -D 63 --policy=fair --mlock -h 20000 -q cyclictest runs in cgroup /test-B tip/sched/core tip/sched/core +this patch cyclictest slice (ms) (default)2.8 8 8 hackbench slice (ms) (default)2.8 20 20 Total Samples | 22679 22595 22686 Average (us) | 84 94(-12%) 59( 37%) Median (P50) (us) | 56 56( 0%) 56( 0%) 90th Percentile (us) | 64 65(- 2%) 63( 3%) 99th Percentile (us) | 1047 1273(-22%) 74( 94%) 99.9th Percentile (us) | 2431 4751(-95%) 663( 86%) Maximum (us) | 4694 8655(-84%) 3934( 55%) Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260410132321.2897789-1-vincent.guittot@linaro.org --- diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 12890ef16603b..f179faf7a6a1e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1116,7 +1116,7 @@ static struct sched_entity *__pick_eevdf(struct cfs_rq *cfs_rq, bool protect) /* * Picking the ->next buddy will affect latency but not fairness. */ - if (sched_feat(PICK_BUDDY) && + if (sched_feat(PICK_BUDDY) && protect && cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next)) { /* ->next will never be delayed */ WARN_ON_ONCE(cfs_rq->next->sched_delayed); @@ -9138,8 +9138,10 @@ pick: return; preempt: - if (preempt_action == PREEMPT_WAKEUP_SHORT) + if (preempt_action == PREEMPT_WAKEUP_SHORT) { cancel_protect_slice(se); + clear_buddies(cfs_rq, se); + } resched_curr_lazy(rq); }