diff options
| author | Vincent Guittot <vincent.guittot@linaro.org> | 2026-01-23 11:28:58 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-01-23 11:53:20 +0100 |
| commit | 15257cc2f905dbf5813c0bfdd3c15885f28093c4 (patch) | |
| tree | 4313c6614389d883c6a8125a760dba81db359cbf /kernel | |
| parent | 4f70f106bca1a56bd66d00830ac91680bd754974 (diff) | |
sched/fair: Revert force wakeup preemption
This agressively bypasses run_to_parity and slice protection with the
assumpiton that this is what waker wants but there is no garantee that
the wakee will be the next to run. It is a better choice to use
yield_to_task or WF_SYNC in such case.
This increases the number of resched and preemption because a task becomes
quickly "ineligible" when it runs; We update the task vruntime periodically
and before the task exhausted its slice or at least quantum.
Example:
2 tasks A and B wake up simultaneously with lag = 0. Both are
eligible. Task A runs 1st and wakes up task C. Scheduler updates task
A's vruntime which becomes greater than average runtime as all others
have a lag == 0 and didn't run yet. Now task A is ineligible because
it received more runtime than the other task but it has not yet
exhausted its slice nor a min quantum. We force preemption, disable
protection but Task B will run 1st not task C.
Sidenote, DELAY_ZERO increases this effect by clearing positive lag at
wake up.
Fixes: e837456fdca8 ("sched/fair: Reimplement NEXT_BUDDY to align with EEVDF goals")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260123102858.52428-1-vincent.guittot@linaro.org
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 10 |
1 files changed, 0 insertions, 10 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a148c61a8085..3eaeceda71b0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8828,16 +8828,6 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int if ((wake_flags & WF_FORK) || pse->sched_delayed) return; - /* - * If @p potentially is completing work required by current then - * consider preemption. - * - * Reschedule if waker is no longer eligible. */ - if (in_task() && !entity_eligible(cfs_rq, se)) { - preempt_action = PREEMPT_WAKEUP_RESCHED; - goto preempt; - } - /* Prefer picking wakee soon if appropriate. */ if (sched_feat(NEXT_BUDDY) && set_preempt_buddy(cfs_rq, wake_flags, pse, se)) { |