linux-kernel - [PATCH v4 3/7] sched/fair: avoid double search on same cpu

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Message-Id: <20220619120451.95251-4-wuyun.abel@bytedance.com>
Date:   Sun, 19 Jun 2022 20:04:47 +0800
From:   Abel Wu <wuyun.abel@...edance.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Josh Don <joshdon@...gle.com>, Chen Yu <yu.c.chen@...el.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        "Gautham R . Shenoy" <gautham.shenoy@....com>,
        linux-kernel@...r.kernel.org, Abel Wu <wuyun.abel@...edance.com>
Subject: [PATCH v4 3/7] sched/fair: avoid double search on same cpu

The prev cpu is checked at the beginning of SIS, and it's unlikely to be
idle before the second check in select_idle_smt(). So we'd better focus
only on its SMT siblings.

Signed-off-by: Abel Wu <wuyun.abel@...edance.com>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e57d7cdf46ce..aba1dad19574 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6290,6 +6290,8 @@ static int select_idle_smt(struct task_struct *p, int target)
 	int cpu;
 
 	for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
+		if (cpu == target)
+			continue;
 		if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
 			return cpu;
 	}
-- 
2.31.1