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Subject[tip:sched/core] sched: Set skip_clock_update in yield_task_fair()
Commit-ID:  916671c08b7808aebec87cc56c85788e665b3c6b
Gitweb: http://git.kernel.org/tip/916671c08b7808aebec87cc56c85788e665b3c6b
Author: Mike Galbraith <mgalbraith@suse.de>
AuthorDate: Tue, 22 Nov 2011 15:21:26 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 6 Dec 2011 09:06:24 +0100

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>
---
kernel/sched/core.c | 7 +++++++
kernel/sched/fair.c | 6 ++++++
2 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ca8fd44..db313c3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4547,6 +4547,13 @@ again:
*/
if (preempt && rq != p_rq)
resched_task(p_rq->curr);
+ } else {
+ /*
+ * We might have set it in task_yield_fair(), but are
+ * not going to schedule(), so don't want to skip
+ * the next update.
+ */
+ rq->skip_clock_update = 0;
}

out:
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8e534a0..81ccb81 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);

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