sched: Cleanup/optimize clock updates

Now that we no longer depend on the clock being updated prior to enqueueing
on migratory wakeup, we can clean up a bit, placing calls to update_rq_clock()
exactly where they are needed, ie on enqueue, dequeue and schedule events.

In the case of a freshly enqueued task immediately preempting, we can skip the
update during preemption, as the clock was just updated by the enqueue event.
We also save an unneeded call during a migratory wakeup by not updating the
previous runqueue, where update_curr() won't be invoked.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301199.6785.32.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 0 insertions, 2 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index c3b69d4b5d65..69e582020ff8 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -3064,8 +3064,6 @@ static void active_load_balance(struct rq *busiest_rq, int busiest_cpu)
 
         /* move a task from busiest_rq to target_rq */
         double_lock_balance(busiest_rq, target_rq);
-        update_rq_clock(busiest_rq);
-        update_rq_clock(target_rq);
 
         /* Search for an sd spanning us and the target CPU. */
         for_each_domain(target_cpu, sd) {