[tip: sched/core] sched/fair: Avoid double search on same cpu

["tip-bot2 for Abel Wu" <tip-bot2@linutronix.de>]

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

Commit-ID:     b9bae70440d21e106fbc098803b5a190df65f2e0
Gitweb:        https://git.kernel.org/tip/b9bae70440d21e106fbc098803b5a190df65f2e0
Author:        Abel Wu <wuyun.abel@bytedance.com>
AuthorDate:    Wed, 07 Sep 2022 19:19:57 +08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 07 Sep 2022 21:53:46 +02:00

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 on its SMT siblings.

Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Don <joshdon@google.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/r/20220907112000.1854-3-wuyun.abel@bytedance.com
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9657c7d..1ad79aa 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6355,6 +6355,8 @@ 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;
 	}