linux-kernel - [PATCH v2]sched:add check of shallowest_idle_cpu before search for least_loaded

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Message-ID: <544E1348.4050100@huawei.com>
Date:	Mon, 27 Oct 2014 17:41:28 +0800
From:	Yao Dongdong <yaodongdong@...wei.com>
To:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	<yaodongdong@...wei.com>
Subject: [PATCH v2]sched:add check of 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: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;
--
1.8.0.1


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