linux-kernel - [PATCH 10/11 v3] sched/fair: Do not try to migrate delayed dequeue task

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Message-ID: <20241202174606.4074512-11-vincent.guittot@linaro.org>
Date: Mon,  2 Dec 2024 18:46:05 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: mingo@...hat.com,
	peterz@...radead.org,
	juri.lelli@...hat.com,
	dietmar.eggemann@....com,
	rostedt@...dmis.org,
	bsegall@...gle.com,
	mgorman@...e.de,
	vschneid@...hat.com,
	linux-kernel@...r.kernel.org
Cc: kprateek.nayak@....com,
	pauld@...hat.com,
	efault@....de,
	luis.machado@....com,
	tj@...nel.org,
	void@...ifault.com,
	Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 10/11 v3] 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@...aro.org>
---
 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 95c51604e1ba..555a9eba5486 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9394,11 +9394,15 @@ 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;
 
-- 
2.43.0