linux-kernel - [tip:sched/core] sched/fair: Avoid an unnecessary lookup of current CPU ID during wake

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Date:   Wed, 21 Feb 2018 02:27:38 -0800
From:   tip-bot for Mel Gorman <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, torvalds@...ux-foundation.org,
        ggherdovich@...e.cz, efault@....de, tglx@...utronix.de,
        mgorman@...hsingularity.net, mingo@...nel.org,
        matt@...eblueprint.co.uk, hpa@...or.com,
        linux-kernel@...r.kernel.org
Subject: [tip:sched/core] sched/fair: Avoid an unnecessary lookup of current
 CPU ID during wake_affine

Commit-ID:  7ebb66a12f85bc375beaf45ca900427fe47aa8f7
Gitweb:     https://git.kernel.org/tip/7ebb66a12f85bc375beaf45ca900427fe47aa8f7
Author:     Mel Gorman <mgorman@...hsingularity.net>
AuthorDate: Tue, 13 Feb 2018 13:37:25 +0000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 21 Feb 2018 08:49:07 +0100

sched/fair: Avoid an unnecessary lookup of current CPU ID during wake_affine

The only caller of wake_affine() knows the CPU ID. Pass it in instead of
rechecking it.

Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Giovanni Gherdovich <ggherdovich@...e.cz>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20180213133730.24064-2-mgorman@techsingularity.net
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/fair.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 820f94c..0132572 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5751,9 +5751,8 @@ wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
 }
 
 static int wake_affine(struct sched_domain *sd, struct task_struct *p,
-		       int prev_cpu, int sync)
+		       int this_cpu, int prev_cpu, int sync)
 {
-	int this_cpu = smp_processor_id();
 	int target = nr_cpumask_bits;
 
 	if (sched_feat(WA_IDLE))
@@ -6376,7 +6375,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
 		if (cpu == prev_cpu)
 			goto pick_cpu;
 
-		new_cpu = wake_affine(affine_sd, p, prev_cpu, sync);
+		new_cpu = wake_affine(affine_sd, p, cpu, prev_cpu, sync);
 	}
 
 	if (sd && !(sd_flag & SD_BALANCE_FORK)) {