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.
>
> Signed-off-by: Kirill V Tkhai <tkhai@xxxxxxxxx>
> CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
> CC: Ingo Molnar <mingo@xxxxxxxxxx>
> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> CC: linux-rt-users <linux-rt-users@xxxxxxxxxxxxxxx>
> ---
> 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)
--
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