linux-kernel - [tip: sched/core] sched/fair: Do strict inequality check for busiest misfit task group

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Message-ID: <170915760926.398.7923117841020138205.tip-bot2@tip-bot2>
Date: Wed, 28 Feb 2024 22:00:09 -0000
From: "tip-bot2 for David Vernet" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: David Vernet <void@...ifault.com>, Ingo Molnar <mingo@...nel.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Valentin Schneider <vschneid@...hat.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Do strict inequality check for busiest
 misfit task group

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

Commit-ID:     7f1a7229718d788f26a711374da83adc2689837f
Gitweb:        https://git.kernel.org/tip/7f1a7229718d788f26a711374da83adc2689837f
Author:        David Vernet <void@...ifault.com>
AuthorDate:    Mon, 05 Feb 2024 22:39:20 -06:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 28 Feb 2024 15:19:24 +01:00

sched/fair: Do strict inequality check for busiest misfit task group

In update_sd_pick_busiest(), when comparing two sched groups that are
both of type group_misfit_task, we currently consider the new group as
busier than the current busiest group even if the new group has the
same misfit task load as the current busiest group. We can avoid some
unnecessary writes if we instead only consider the newest group to be
the busiest if it has a higher load than the current busiest. This
matches the behavior of other group types where we compare load, such as
two groups that are both overloaded.

Let's update the group_misfit_task type comparison to also only update
the busiest group in the event of strict inequality.

Signed-off-by: David Vernet <void@...ifault.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
Reviewed-by: Valentin Schneider <vschneid@...hat.com>
Link: https://lore.kernel.org/r/20240206043921.850302-3-void@manifault.com
---
 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 41dda53..448520f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10032,7 +10032,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
 		 * If we have more than one misfit sg go with the biggest
 		 * misfit.
 		 */
-		if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
+		if (sgs->group_misfit_task_load <= busiest->group_misfit_task_load)
 			return false;
 		break;