linux-kernel - [PATCH v3 1/3] sched: remove one division operation in find_buiest

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Date:	Tue,  6 Aug 2013 17:36:41 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Mike Galbraith <efault@....de>,
	Paul Turner <pjt@...gle.com>, Alex Shi <alex.shi@...el.com>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Namhyung Kim <namhyung@...nel.org>,
	Joonsoo Kim <js1304@...il.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH v3 1/3] sched: remove one division operation in find_buiest_queue()

Remove one division operation in find_buiest_queue().

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9565645..52898dc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4968,7 +4968,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 				     struct sched_group *group)
 {
 	struct rq *busiest = NULL, *rq;
-	unsigned long max_load = 0;
+	unsigned long busiest_load = 0, busiest_power = SCHED_POWER_SCALE;
 	int i;
 
 	for_each_cpu(i, sched_group_cpus(group)) {
@@ -4999,10 +4999,9 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 		 * the load can be moved away from the cpu that is potentially
 		 * running at a lower capacity.
 		 */
-		wl = (wl * SCHED_POWER_SCALE) / power;
-
-		if (wl > max_load) {
-			max_load = wl;
+		if (wl * busiest_power > busiest_load * power) {
+			busiest_load = wl;
+			busiest_power = power;
 			busiest = rq;
 		}
 	}
-- 
1.7.9.5

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