[tip:sched/core] sched: Check if we got a shallowest_idle_cpu before searching for least_loaded_cpu

[tip-bot for Yao Dongdong <tipbot@zytor.com>]

Commit-ID:  9f96742a13135e6c609cc99a3a458402af3c8f31
Gitweb:     http://git.kernel.org/tip/9f96742a13135e6c609cc99a3a458402af3c8f31
Author:     Yao Dongdong <yaodongdong@huawei.com>
AuthorDate: Tue, 28 Oct 2014 04:08:06 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 4 Nov 2014 07:17:51 +0100

sched: Check if we got a shallowest_idle_cpu before searching 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@huawei.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1414469286-6023-1-git-send-email-yaodongdong@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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 ec32c26d..d03d76d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4641,7 +4641,7 @@ 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;