linux-kernel - [PATCH resend] sched:check if got a shallowest_idle_cpu before search for least_loaded

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Date:	Tue, 28 Oct 2014 04:08:06 +0000
From:	Yao Dongdong <yaodongdong@...wei.com>
To:	<peterz@...radead.org>, <mingo@...hat.com>
CC:	<linux-kernel@...r.kernel.org>, <srikar@...ux.vnet.ibm.com>,
	<yaodongdong@...wei.com>
Subject: [PATCH resend] sched:check if got a shallowest_idle_cpu before search for least_loaded_cpu

Idle cpu is idler than non-idle cpu, so we needn't search for least_loaded_cpu
after we have found an idle cpu.

Signed-off-by: Yao Dongdong <yaodongdong@...wei.com>
Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.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 0b069bf..2445a23 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4446,7 +4446,7 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
 				latest_idle_timestamp = rq->idle_stamp;
 				shallowest_idle_cpu = i;
 			}
-		} else {
+		} else if (shallowest_idle_cpu == -1) {
 			load = weighted_cpuload(i);
 			if (load < min_load || (load == min_load && i == this_cpu)) {
 				min_load = load;
-- 
1.8.3.4

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