On Thu, 5 Feb 2015 23:59:33 +0800
Xunlei Pang <xlp...@126.com> wrote:
return p;
> @@ -1886,28 +1892,73 @@ static void set_cpus_allowed_rt(struct task_struct *p,
> const struct cpumask *new_mask)
> {
> struct rq *rq;
> - int weight;
> + int old_weight, new_weight;
> + int preempt_push = 0, direct_push = 0;
>
> BUG_ON(!rt_task(p));
>
> if (!task_on_rq_queued(p))
> return;
>
> - weight = cpumask_weight(new_mask);
> + old_weight = p->nr_cpus_allowed;
> + new_weight = cpumask_weight(new_mask);
> +
> + rq = task_rq(p);
> +
> + if (new_weight > 1 &&
> + rt_task(rq->curr) &&
> + !test_tsk_need_resched(rq->curr)) {
> + /*
> + * Set new mask information which is already valid
> + * to prepare pushing.
> + *
> + * We own p->pi_lock and rq->lock. rq->lock might
> + * get released when doing direct pushing, however
> + * p->pi_lock is always held, so it's safe to assign
> + * the new_mask and new_weight to p.
> + */
> + cpumask_copy(&p->cpus_allowed, new_mask);
> + p->nr_cpus_allowed = new_weight;
> +
> + if (task_running(rq, p) &&
> + cpumask_test_cpu(task_cpu(p), new_mask) &&
Why the check for task_cpu being in new_mask?
> + cpupri_find(&rq->rd->cpupri, p, NULL)) {
> + /*
> + * At this point, current task gets migratable most
> + * likely due to the change of its affinity, let's
> + * figure out if we can migrate it.
> + *
> + * Is there any task with the same priority as that
> + * of current task? If found one, we should resched.
> + * NOTE: The target may be unpushable.
> + */
> + if (p->prio == rq->rt.highest_prio.next) {
> + /* One target just in pushable_tasks list. */
> + requeue_task_rt(rq, p, 0);
> + preempt_push = 1;
> + } else if (rq->rt.rt_nr_total > 1) {
> + struct task_struct *next;
> +
> + requeue_task_rt(rq, p, 0);
> + next = peek_next_task_rt(rq);
> + if (next != p && next->prio == p->prio)
> + preempt_push = 1;
> + }
> + } else if (!task_running(rq, p))
> + direct_push = 1;
We could avoid the second check (!task_running()) by splitting up the
first if:
if (task_running(rq, p)) {
if (cpumask_test_cpu() && cpupri_find()) {
}
} else {
direct push = 1
Also, is the copy of cpus_allowed only done so that cpupri_find is
called? If so maybe move it in there too:
if (task_running(rq, p)) {
if (!cpumask_test_cpu())
goto update;
cpumask_copy(&p->cpus_allowed, new_mask);
p->nr_cpus_allowed = new_weight;
if (!cpupri_find())
goto update;
[...]
This way we avoid the double copy of cpumask unless we truly need to do
it.
> + }
>
> /*
> * Only update if the process changes its state from whether it
> * can migrate or not.
> */
> - if ((p->nr_cpus_allowed > 1) == (weight > 1))
> - return;
> -
> - rq = task_rq(p);
> + if ((old_weight > 1) == (new_weight > 1))
> + goto out;
>
> /*
> * The process used to be able to migrate OR it can now migrate
> */
> - if (weight <= 1) {
> + if (new_weight <= 1) {
> if (!task_current(rq, p))
> dequeue_pushable_task(rq, p);
> BUG_ON(!rq->rt.rt_nr_migratory);
> @@ -1919,6 +1970,15 @@ static void set_cpus_allowed_rt(struct task_struct *p,
> }
>
> update_rt_migration(&rq->rt);
> +
> +out:
> + BUG_ON(direct_push == 1 && preempt_push == 1);
Do we really need this bug on?
> +
> + if (direct_push)
> + push_rt_tasks(rq);
> +
> + if (preempt_push)
We could make that an "else if" if they really are mutually exclusive.
-- Steve
> + resched_curr(rq);
> }
>
> /* Assumes rq->lock is held */
--
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