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sched/fair: Implement DELAY_ZERO

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'Extend' DELAY_DEQUEUE by noting that since we wanted to dequeued them
at the 0-lag point, truncate lag (eg. don't let them earn positive
lag).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105030.403750550@infradead.org
This commit is contained in:
Peter Zijlstra 2024-05-23 12:26:06 +02:00
parent 152e11f6df
commit 54a58a7877
2 changed files with 21 additions and 2 deletions
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20
kernel/sched/fair.c
View File

@ -5447,8 +5447,11 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
update_min_vruntime(cfs_rq);
if (flags & DEQUEUE_DELAYED)
if (flags & DEQUEUE_DELAYED) {
se->sched_delayed = 0;
if (sched_feat(DELAY_ZERO) && se->vlag > 0)
se->vlag = 0;
}
if (cfs_rq->nr_running == 0)
update_idle_cfs_rq_clock_pelt(cfs_rq);
@ -5527,7 +5530,6 @@ pick_next_entity(struct rq *rq, struct cfs_rq *cfs_rq)
dequeue_entities(rq, se, DEQUEUE_SLEEP | DEQUEUE_DELAYED);
SCHED_WARN_ON(se->sched_delayed);
SCHED_WARN_ON(se->on_rq);
return NULL;
}
return se;
@ -6825,6 +6827,20 @@ requeue_delayed_entity(struct sched_entity *se)
SCHED_WARN_ON(!se->sched_delayed);
SCHED_WARN_ON(!se->on_rq);
if (sched_feat(DELAY_ZERO)) {
update_entity_lag(cfs_rq, se);
if (se->vlag > 0) {
cfs_rq->nr_running--;
if (se != cfs_rq->curr)
__dequeue_entity(cfs_rq, se);
se->vlag = 0;
place_entity(cfs_rq, se, 0);
if (se != cfs_rq->curr)
__enqueue_entity(cfs_rq, se);
cfs_rq->nr_running++;
}
}
se->sched_delayed = 0;
}

3
kernel/sched/features.h
View File

@ -34,8 +34,11 @@ SCHED_FEAT(CACHE_HOT_BUDDY, true)
* By delaying the dequeue for non-eligible tasks, they remain in the
* competition and can burn off their negative lag. When they get selected
* they'll have positive lag by definition.
*
* DELAY_ZERO clips the lag on dequeue (or wakeup) to 0.
*/
SCHED_FEAT(DELAY_DEQUEUE, true)
SCHED_FEAT(DELAY_ZERO, true)
/*
* Allow wakeup-time preemption of the current task: