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SubjectRe: [PATCH RFC] sched/fair: fix sudden expiration of cfq quota in put_prev_task()
On 07.04.2015 18:12, Peter Zijlstra wrote:
> On Tue, Apr 07, 2015 at 03:47:58PM +0200, Peter Zijlstra wrote:
>> Lemme think a bit more on that.
>
> So going by 734ff2a71f9e ("sched/rt: Fix picking RT and DL tasks from
> empty queue") something like this would be called for.
>
> ---
> kernel/sched/fair.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index fdae26eb7218..1e47f816c976 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5175,6 +5175,21 @@ pick_next_task_fair(struct rq *rq, struct task_struct *prev)
> return p;
> simple:
> cfs_rq = &rq->cfs;

We don't need this if prev isn't from fair_sched_class:
first "goto simple" should go directly to "if (!cfs_rq->nr_running)".

> +
> + if (cfs_bandwidth_used()) {
> + /*
> + * We may dequeue prev's cfs_rq in put_prev_task().
> + * So, we update time before cfs_rq->nr_running check.
> + */
> + if (prev->on_rq)
> + update_curr(cfs_rq);
> +
> + se = &prev->se;
> + for_each_sched_entity(se) {

Probably update_curr() should be inside loop too?

> + cfs_rq = cfs_rq_of(se);
> + check_cfs_rq_runtime(cfs_rq);
> + }
> + }
> #endif
>
> if (!cfs_rq->nr_running)
>


--
Konstantin


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