linux-kernel - [PATCH] sched/fair: Optimize vlag entity placement

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Message-ID: <20240704092345.51644-1-sieberf@amazon.com>
Date: Thu, 4 Jul 2024 11:23:45 +0200
From: Fernand Sieber <sieberf@...zon.com>
To:
CC: <linux-kernel@...r.kernel.org>, Fernand Sieber <sieberf@...zon.com>, "Ingo
 Molnar" <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Juri Lelli
	<juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH] sched/fair: Optimize vlag entity placement

Optimize for common path when placing an entity with no lag.
Since adjusting a zero lag is always going to produce a zero lag regardless
of the local load, don't bother about calaculating the adjusting factor.

Signed-off-by: Fernand Sieber <sieberf@...zon.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Vincent Guittot <vincent.guittot@...aro.org>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8a5b1ae0aa55..e78272c87274 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5190,7 +5190,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 	 *
 	 * EEVDF: placement strategy #1 / #2
 	 */
-	if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) {
+	if (se->vlag && sched_feat(PLACE_LAG) && cfs_rq->nr_running) {
 		struct sched_entity *curr = cfs_rq->curr;
 		unsigned long load;
 
-- 
2.40.1