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| author | Dave Kleikamp <dave.kleikamp@oracle.com> | 2017-05-15 14:14:13 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-05-23 10:01:34 +0200 |
| commit | c249f255aab86b9b187ba319b9d2684841ac7c8d (patch) | |
| tree | 995fbe15e1c550ea496acebb8fc1c874b24f989c | |
| parent | 896bbb2522587e3b8eb2a0d204d43ccc1042a00d (diff) | |
| download | linux-c249f255aab86b9b187ba319b9d2684841ac7c8d.tar.gz | |
sched/rt: Minimize rq->lock contention in do_sched_rt_period_timer()
With CONFIG_RT_GROUP_SCHED=y, do_sched_rt_period_timer() sequentially takes each CPU's rq->lock. On a large, busy system, the cumulative time it takes to acquire each lock can be excessive, even triggering a watchdog timeout. If rt_rq->rt_time and rt_rq->rt_nr_running are both zero, this function does nothing while holding the lock, so don't bother taking it at all. Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/a767637b-df85-912f-ba69-c90ee00a3fb6@oracle.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | kernel/sched/rt.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index c18b50094fab..581d5c7a5264 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -840,6 +840,17 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun) int enqueue = 0; struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i); struct rq *rq = rq_of_rt_rq(rt_rq); + int skip; + + /* + * When span == cpu_online_mask, taking each rq->lock + * can be time-consuming. Try to avoid it when possible. + */ + raw_spin_lock(&rt_rq->rt_runtime_lock); + skip = !rt_rq->rt_time && !rt_rq->rt_nr_running; + raw_spin_unlock(&rt_rq->rt_runtime_lock); + if (skip) + continue; raw_spin_lock(&rq->lock); if (rt_rq->rt_time) { |