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authorPeter Zijlstra <peterz@infradead.org>2015-01-05 11:18:11 +0100
committerIngo Molnar <mingo@kernel.org>2015-01-14 13:34:20 +0100
commit9edfbfed3f544a7830d99b341f0c175995a02950 (patch)
tree58e117b481cc0fdfd9f4595d3fa73e66c689547a /kernel/sched/rt.c
parentcebde6d681aa45f96111cfcffc1544cf2a0454ff (diff)
downloadop-kernel-dev-9edfbfed3f544a7830d99b341f0c175995a02950.zip
op-kernel-dev-9edfbfed3f544a7830d99b341f0c175995a02950.tar.gz
sched/core: Rework rq->clock update skips
The original purpose of rq::skip_clock_update was to avoid 'costly' clock updates for back to back wakeup-preempt pairs. The big problem with it has always been that the rq variable is unaware of the context and causes indiscrimiate clock skips. Rework the entire thing and create a sense of context by only allowing schedule() to skip clock updates. (XXX can we measure the cost of the added store?) By ensuring only schedule can ever skip an update, we guarantee we're never more than 1 tick behind on the update. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: umgwanakikbuti@gmail.com Link: http://lkml.kernel.org/r/20150105103554.432381549@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/rt.c')
-rw-r--r--kernel/sched/rt.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index ee15f5a..6725e3c 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -831,11 +831,14 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
enqueue = 1;
/*
- * Force a clock update if the CPU was idle,
- * lest wakeup -> unthrottle time accumulate.
+ * When we're idle and a woken (rt) task is
+ * throttled check_preempt_curr() will set
+ * skip_update and the time between the wakeup
+ * and this unthrottle will get accounted as
+ * 'runtime'.
*/
if (rt_rq->rt_nr_running && rq->curr == rq->idle)
- rq->skip_clock_update = -1;
+ rq_clock_skip_update(rq, false);
}
if (rt_rq->rt_time || rt_rq->rt_nr_running)
idle = 0;
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