[tip: sched/core] sched/fair: Do not try to migrate delayed dequeue task

[tip-bot2 for Vincent Guittot]

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

Commit-ID:     61b82dfb6b7e1f951fd1e95198a2aee2ccf6a167
Gitweb:        https://git.kernel.org/tip/61b82dfb6b7e1f951fd1e95198a2aee2ccf6a167
Author:        Vincent Guittot <vincent.guittot@xxxxxxxxxx>
AuthorDate:    Mon, 02 Dec 2024 18:46:05 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 09 Dec 2024 11:48:13 +01:00

sched/fair: Do not try to migrate delayed dequeue task

Migrating a delayed dequeued task doesn't help in balancing the number
of runnable tasks in the system.

Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Link: https://lore.kernel.org/r/20241202174606.4074512-11-vincent.guittot@xxxxxxxxxx
---
 kernel/sched/fair.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 84c0191..2aa1d0c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9391,11 +9391,15 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
 
 	/*
 	 * We do not migrate tasks that are:
-	 * 1) throttled_lb_pair, or
-	 * 2) cannot be migrated to this CPU due to cpus_ptr, or
-	 * 3) running (obviously), or
-	 * 4) are cache-hot on their current CPU.
+	 * 1) delayed dequeued unless we migrate load, or
+	 * 2) throttled_lb_pair, or
+	 * 3) cannot be migrated to this CPU due to cpus_ptr, or
+	 * 4) running (obviously), or
+	 * 5) are cache-hot on their current CPU.
 	 */
+	if ((p->se.sched_delayed) && (env->migration_type != migrate_load))
+		return 0;
+
 	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
 		return 0;