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SubjectRe: [PATCH 2/2] rt: Increase/decrease the nr of migratory tasks when enabling/disabling migration

* Daniel Bristot de Oliveira <bristot@redhat.com> wrote:

> On 06/22/2017 09:49 PM, Ingo Molnar wrote:
> > So AFAICS it's this block that is used twice:
> >
> >>>> + rq = task_rq_lock(p, &rf);
> >>>> + p->nr_cpus_allowed = cpumask_weight(&p->cpus_mask);
> >>>> + if (unlikely((p->sched_class == &rt_sched_class ||
> >>>> + p->sched_class == &dl_sched_class) &&
> >>>> + p->nr_cpus_allowed > 1)) {
> >>>> + if (p->sched_class == &rt_sched_class)
> >>>> + task_rq(p)->rt.rt_nr_migratory++;
> >>>> + else
> >>>> + task_rq(p)->dl.dl_nr_migratory++;
> >>>> + }
> >>>> + task_rq_unlock(rq, p, &rf);
> > or is there some difference I haven't noticed?
>
> One block increases the number of migratory tasks, and the
> other one decreases...
>
> How about this version? (if it is good, I will polish it in a v2).
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ce34e4f..0f66376 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7566,10 +7566,57 @@ const u32 sched_prio_to_wmult[40] = {
>
> #if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_SMP)
>
> +enum inc_dec_migratory {
> + DEC_NR_MIGRATORY = -1,
> + INC_NR_MIGRATORY = 1,
> +};
> +
> +static inline void
> +inc_dec_nr_migratory(struct task_struct *p, enum inc_dec_migratory id)
> +{
> + if (unlikely((p->sched_class == &rt_sched_class ||
> + p->sched_class == &dl_sched_class) &&
> + p->nr_cpus_allowed > 1)) {
> + if (p->sched_class == &rt_sched_class)
> + task_rq(p)->rt.rt_nr_migratory += id;
> + else
> + task_rq(p)->dl.dl_nr_migratory += id;
> + }
> +}

How about just 'long delta', pass in +1 or -1 and do away with the
inc_dec_migratory complication?

Thanks,

Ingo

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