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| author | Peter Zijlstra <peterz@infradead.org> | 2024-11-29 11:15:41 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-02-08 10:00:57 +0100 |
| commit | 673e5f00a74bc91d29af0dec527b8625d4dc4a60 (patch) | |
| tree | de1f93feb2efed3998de68073d7297b4b7e0f928 /kernel | |
| parent | fd8b624505cd3749d75d0fd7680574e39f761def (diff) | |
| download | linux-673e5f00a74bc91d29af0dec527b8625d4dc4a60.tar.gz linux-673e5f00a74bc91d29af0dec527b8625d4dc4a60.tar.bz2 linux-673e5f00a74bc91d29af0dec527b8625d4dc4a60.zip | |
sched/fair: Untangle NEXT_BUDDY and pick_next_task()
[ Upstream commit 2a77e4be12cb58bbf774e7c717c8bb80e128b7a4 ]
There are 3 sites using set_next_buddy() and only one is conditional
on NEXT_BUDDY, the other two sites are unconditional; to note:
- yield_to_task()
- cgroup dequeue / pick optimization
However, having NEXT_BUDDY control both the wakeup-preemption and the
picking side of things means its near useless.
Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20241129101541.GA33464@noisy.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 4 | ||||
| -rw-r--r-- | kernel/sched/features.h | 9 |
2 files changed, 11 insertions, 2 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 26958431deb7..808010430a16 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5538,9 +5538,9 @@ static struct sched_entity * pick_next_entity(struct rq *rq, struct cfs_rq *cfs_rq) { /* - * Enabling NEXT_BUDDY will affect latency but not fairness. + * Picking the ->next buddy will affect latency but not fairness. */ - if (sched_feat(NEXT_BUDDY) && + if (sched_feat(PICK_BUDDY) && cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next)) { /* ->next will never be delayed */ SCHED_WARN_ON(cfs_rq->next->sched_delayed); diff --git a/kernel/sched/features.h b/kernel/sched/features.h index a3d331dd2d8f..3c12d9f93331 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -32,6 +32,15 @@ SCHED_FEAT(PREEMPT_SHORT, true) SCHED_FEAT(NEXT_BUDDY, false) /* + * Allow completely ignoring cfs_rq->next; which can be set from various + * places: + * - NEXT_BUDDY (wakeup preemption) + * - yield_to_task() + * - cgroup dequeue / pick + */ +SCHED_FEAT(PICK_BUDDY, true) + +/* * Consider buddies to be cache hot, decreases the likeliness of a * cache buddy being migrated away, increases cache locality. */ |