linux-kernel - [PATCH v3 7/7] sched: use per-cpu variable cpumask_weight

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Date:   Wed, 26 Jun 2019 18:29:19 -0700
From:   subhra mazumdar <subhra.mazumdar@...cle.com>
To:     linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, mingo@...hat.com, tglx@...utronix.de,
        steven.sistare@...cle.com, dhaval.giani@...cle.com,
        daniel.lezcano@...aro.org, vincent.guittot@...aro.org,
        viresh.kumar@...aro.org, tim.c.chen@...ux.intel.com,
        mgorman@...hsingularity.net
Subject: [PATCH v3 7/7] sched: use per-cpu variable cpumask_weight_sibling

Use per-cpu var cpumask_weight_sibling for quick lookup in select_idle_cpu.
This is the fast path of scheduler and every cycle is worth saving. Usage
of cpumask_weight can result in iterations.

Signed-off-by: subhra mazumdar <subhra.mazumdar@...cle.com>
---
 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 6a74808..878f11c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6206,7 +6206,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 
 	if (sched_feat(SIS_PROP)) {
 		u64 span_avg = sd->span_weight * avg_idle;
-		floor = cpumask_weight(topology_sibling_cpumask(target));
+		floor = topology_sibling_weight(target);
 		if (floor < 2)
 			floor = 2;
 		limit = floor << 1;
-- 
2.9.3