Re: [PATCH]sched/rt: Do not try to push tasks if pinned task switches to RT
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2013-01-29 13:26:06
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On Tue, 2013-01-29 at 00:23 +0400, Kirill Tkhai wrote:
Just switched pinned task is not able to be pushed. If the rq had had several RT tasks before they have already been considered as candidates to be pushed (or pulled).
Thanks, but I have one minor nit.
quoted hunk ↗ jump to hunk
Signed-off-by: Kirill V Tkhai <redacted> CC: Steven Rostedt <rostedt@goodmis.org> CC: Ingo Molnar <mingo@kernel.org> CC: Peter Zijlstra <peterz@infradead.org> CC: linux-rt-users <redacted> --- kernel/sched/rt.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 4e8f0f4..5f7d92b 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c@@ -1925,9 +1925,9 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p) */ if (p->on_rq && rq->curr != p) { #ifdef CONFIG_SMP - if (rq->rt.overloaded && push_rt_task(rq) && + if (rq->rt.overloaded && p->nr_cpus_allowed > 1 &&
I would swap the order here. That is, check p->nr_cpus_allowed before rq->rt.overloaded. The order doesn't really matter, and even though rq->rt.overloaded is probably more likely to be 0, it is used by other CPUs. And as a micro-optimization, I rather read something that is used by only one CPU than to read something that may be modified by many CPUs. -- Steve
/* Don't resched if we changed runqueues */ - rq != task_rq(p)) + push_rt_task(rq) && rq != task_rq(p)) check_resched = 0; #endif /* CONFIG_SMP */ if (check_resched && p->prio < rq->curr->prio)