From: Mel Gorman <mgorman@techsingularity.net>
Date: Mon, 30 Nov 2020 14:40:20 +0000 (+0000)
Subject: sched/fair: Clear SMT siblings after determining the core is not idle
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=13d5a5e9f9b8515da3c04305ae1bb03ab91be7a7;p=linux.git

sched/fair: Clear SMT siblings after determining the core is not idle

The clearing of SMT siblings from the SIS mask before checking for an idle
core is a small but unnecessary cost. Defer the clearing of the siblings
until the scan moves to the next potential target. The cost of this was
not measured as it is borderline noise but it should be self-evident.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20201130144020.GS3371@techsingularity.net
---

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f5dcedacc1043..efac224c703fd 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6086,10 +6086,11 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
 				break;
 			}
 		}
-		cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
 
 		if (idle)
 			return core;
+
+		cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
 	}
 
 	/*