[tip: sched/core] sched/eevdf: Cancel slice protection if short slice task is eligible

[tip-bot2 for Vincent Guittot]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     ba0d3bf5f97b74ee1cf8ea6cc35efe5a052514a4
Gitweb:        https://git.kernel.org/tip/ba0d3bf5f97b74ee1cf8ea6cc35efe5a052514a4
Author:        Vincent Guittot <vincent.guittot@xxxxxxxxxx>
AuthorDate:    Wed, 24 Jun 2026 17:12:27 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 30 Jun 2026 10:56:55 +02:00

sched/eevdf: Cancel slice protection if short slice task is eligible

If a short slice task will not be the next to be picked but is eligible,
we cancel the slice protection to speedup the time when the short slice
task will be the next to run.

Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Link: https://patch.msgid.link/20260624151229.1710703-5-vincent.guittot@xxxxxxxxxx
---
 kernel/sched/fair.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index af207f0..9046b2e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9859,18 +9859,13 @@ static void wakeup_preempt_fair(struct rq *rq, struct task_struct *p, int wake_f
 	cse_is_idle = se_is_idle(se);
 	pse_is_idle = se_is_idle(pse);
 
+	nse = se;
 	/*
 	 * Preempt an idle entity in favor of a non-idle entity (and don't preempt
 	 * in the inverse case).
 	 */
-	if (cse_is_idle && !pse_is_idle) {
-		/*
-		 * When non-idle entity preempt an idle entity,
-		 * don't give idle entity slice protection.
-		 */
-		preempt_action = PREEMPT_WAKEUP_SHORT;
+	if (cse_is_idle && !pse_is_idle)
 		goto preempt;
-	}
 
 	if (cse_is_idle != pse_is_idle)
 		return;
@@ -9933,16 +9928,23 @@ pick:
 			goto preempt;
 	}
 
+	/*
+	 * If @p is eligible but not the next task to run then cancel protection
+	 * to prevent large scheduling latency
+	 */
+	if (preempt_action == PREEMPT_WAKEUP_SHORT && entity_eligible(cfs_rq, pse))
+		goto preempt;
+
 	if (sched_feat(RUN_TO_PARITY))
 		update_protect_slice(cfs_rq, se);
 
 	return;
 
 preempt:
-	if (preempt_action == PREEMPT_WAKEUP_SHORT) {
-		cancel_protect_slice(se);
+	cancel_protect_slice(se);
+
+	if (preempt_action == PREEMPT_WAKEUP_SHORT)
 		set_short_buddy(cfs_rq, pse);
-	}
 
 	resched_curr_lazy(rq);
 }