diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2024-11-29 11:15:41 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-02-08 09:56:53 +0100 |
| commit | e4b64d34a48c29ad48dbf7466e15fd94a9038586 (patch) | |
| tree | 72d4854c70758d00a859c4b103b3b10fdee5c178 | |
| parent | d4ac1009486923c9394f5397e6477b0a119fb47c (diff) | |
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>
| -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 60be5f8bbe71..a21110b220b7 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5647,9 +5647,9 @@ 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 290874079f60..050d7503064e 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. */ |