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

From: Daniel Bristot de Oliveira
Date: Thu Jun 22 2017 - 09:31:34 EST


On 06/22/2017 10:38 AM, Ingo Molnar wrote:
>
> * Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> wrote:
>
>> void migrate_disable(void)
>> {
>> struct task_struct *p = current;
>> + struct rq *rq;
>> + struct rq_flags rf;
>> +
>>
>> if (in_atomic() || irqs_disabled()) {
>> #ifdef CONFIG_SCHED_DEBUG
>> @@ -7593,10 +7596,21 @@ void migrate_disable(void)
>> preempt_disable();
>> preempt_lazy_disable();
>> pin_current_cpu();
>> - p->migrate_disable = 1;
>>
>> - p->cpus_ptr = cpumask_of(smp_processor_id());
>> + rq = task_rq_lock(p, &rf);
>> + 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--;
>> + }
>> p->nr_cpus_allowed = 1;
>> + task_rq_unlock(rq, p, &rf);
>> + p->cpus_ptr = cpumask_of(smp_processor_id());
>> + p->migrate_disable = 1;
>> +
>>
>> preempt_enable();
>> }
>> @@ -7605,6 +7619,9 @@ EXPORT_SYMBOL(migrate_disable);
>> void migrate_enable(void)
>> {
>> struct task_struct *p = current;
>> + struct rq *rq;
>> + struct rq_flags rf;
>> +
>>
>> if (in_atomic() || irqs_disabled()) {
>> #ifdef CONFIG_SCHED_DEBUG
>> @@ -7628,17 +7645,24 @@ void migrate_enable(void)
>>
>> preempt_disable();
>>
>> - p->cpus_ptr = &p->cpus_mask;
>> - p->nr_cpus_allowed = cpumask_weight(&p->cpus_mask);
>> p->migrate_disable = 0;
>> + p->cpus_ptr = &p->cpus_mask;
>>
>> - if (p->migrate_disable_update) {
>> - struct rq *rq;
>> - struct rq_flags rf;
>> + 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);
>
> The fix looks good to me, but AFAICS the repeat pattern introduced here could be
> factored out into a helper function instead, right?

Like:

static inline int task_in_rt_class(struct task_struct *p)
{
return p->sched_class == &rt_sched_class;
}

static inline int task_in_dl_class(struct task_struct *p)
{
return p->sched_class == &dl_sched_class;
}

?

Thanks!

-- Daniel