linux-kernel - [tip: sched/core] sched/fair: Avoid a second scan of target in select_idle

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Message-ID: <162815607370.395.4560583728552595431.tip-bot2@tip-bot2>
Date:   Thu, 05 Aug 2021 09:34:33 -0000
From:   "tip-bot2 for Mel Gorman" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Mel Gorman <mgorman@...hsingularity.net>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Avoid a second scan of target in
 select_idle_cpu

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

Commit-ID:     56498cfb045d7147cdcba33795d19429afcd1d00
Gitweb:        https://git.kernel.org/tip/56498cfb045d7147cdcba33795d19429afcd1d00
Author:        Mel Gorman <mgorman@...hsingularity.net>
AuthorDate:    Wed, 04 Aug 2021 12:58:57 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 04 Aug 2021 15:16:44 +02:00

sched/fair: Avoid a second scan of target in select_idle_cpu

When select_idle_cpu starts scanning for an idle CPU, it starts with
a target CPU that has already been checked by select_idle_sibling.
This patch starts with the next CPU instead.

Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20210804115857.6253-3-mgorman@techsingularity.net
---
 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 7ee394b..47a0fbf 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6220,7 +6220,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool 
 		time = cpu_clock(this);
 	}
 
-	for_each_cpu_wrap(cpu, cpus, target) {
+	for_each_cpu_wrap(cpu, cpus, target + 1) {
 		if (has_idle_core) {
 			i = select_idle_core(p, cpu, cpus, &idle_cpu);
 			if ((unsigned int)i < nr_cpumask_bits)