sched: Set skip_clock_update in yield_task_fair()

This is another case where we are on our way to schedule(),
so can save a useless clock update and resulting microscopic
vruntime update.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1321971686.6855.18.camel@marge.simson.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 0 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8e534a05e3ed..81ccb811afb4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3075,6 +3075,12 @@ static void yield_task_fair(struct rq *rq)
 		 * Update run-time statistics of the 'current'.
 		 */
 		update_curr(cfs_rq);
+		/*
+		 * Tell update_rq_clock() that we've just updated,
+		 * so we don't do microscopic update in schedule()
+		 * and double the fastpath cost.
+		 */
+		 rq->skip_clock_update = 1;
 	}
 
 	set_skip_buddy(se);