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sched/rt: small optimization to update_curr_rt() 

Impact: micro-optimization to SCHED_FIFO/RR scheduling

A very minor improvement, but might it be better to check sched_rt_runtime(rt_rq)
before taking the rt_runtime_lock?

Peter Zijlstra observes:

> Yes, I think its ok to do so.
>
> Like pointed out in the other thread, there are two races:
>
>  - sched_rt_runtime() going to RUNTIME_INF, and that will be handled
>    properly by sched_rt_runtime_exceeded()
>
>  - sched_rt_runtime() going to !RUNTIME_INF, and here we can miss an
>    accounting cycle, but I don't think that is something to worry too
>    much about.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

--

 kernel/sched_rt.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
This commit is contained in:
Dimitri Sivanich 2008-10-31 08:03:41 -05:00 committed by Ingo Molnar
parent 45beca08dd
commit e113a745f6
1 changed files with 2 additions and 2 deletions
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4
kernel/sched_rt.c
View File

@ -537,13 +537,13 @@ static void update_curr_rt(struct rq *rq)
for_each_sched_rt_entity(rt_se) {
rt_rq = rt_rq_of_se(rt_se);
spin_lock(&rt_rq->rt_runtime_lock);
if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
spin_lock(&rt_rq->rt_runtime_lock);
rt_rq->rt_time += delta_exec;
if (sched_rt_runtime_exceeded(rt_rq))
resched_task(curr);
spin_unlock(&rt_rq->rt_runtime_lock);
}
spin_unlock(&rt_rq->rt_runtime_lock);
}
}