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Message-ID: <b647ffbd0807140750r54e5139aj7b25a28ef7ca247e@mail.gmail.com>
Date: Mon, 14 Jul 2008 16:50:41 +0200
From: "Dmitry Adamushko" <dmitry.adamushko@...il.com>
To: "Gregory Haskins" <ghaskins@...ell.com>
Cc: "Steven Rostedt" <rostedt@...dmis.org>,
"Ingo Molnar" <mingo@...e.hu>,
"Thomas Gleixner" <tglx@...utronix.de>,
"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [sched-devel, patch-rfc] rework #2 of "prioritize non-migratable tasks over migratable ones"
2008/7/1 Dmitry Adamushko <dmitry.adamushko@...il.com>:
>
> Finally, this new version compiles and boots (applied a minor compilation fix).
> Functionality is not yet fully tested though.
>
> It's on top of today's tip tree.
>
> Any objections to this approach?
[ ping ]
Gregory or anyone else, any feedback on this one?
TIA,
>
> ---
> From: Dmitry Adamushko <dmitry.adamushko@...il.com>
> Subject: prioritize non-migratable tasks over migratable ones in a generic way
>
> (1) handle in a generic way all cases when a newly woken-up task is
> not migratable (not just a corner case when "rt_se->nr_cpus_allowed ==
> 1")
>
> (2) if current is to be preempted, then make sure "p" will be picked
> up by pick_next_task_rt().
> i.e. move task's group at the head of its list as well.
>
> currently, it's not a case for the group-scheduling case as described
> here: http://www.ussg.iu.edu/hypermail/linux/kernel/0807.0/0134.html
>
>
> Signed-off-by: Dmitry Adamushko <dmitry.adamushko@...il.com>
>
> ---
> diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
> index 7c96147..7bc73e8 100644
> --- a/kernel/sched_rt.c
> +++ b/kernel/sched_rt.c
> @@ -599,11 +599,7 @@ static void __enqueue_rt_entity(struct sched_rt_entity *rt_se)
> if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
> return;
>
> - if (rt_se->nr_cpus_allowed == 1)
> - list_add(&rt_se->run_list, queue);
> - else
> - list_add_tail(&rt_se->run_list, queue);
> -
> + list_add_tail(&rt_se->run_list, queue);
> __set_bit(rt_se_prio(rt_se), array->bitmap);
>
> inc_rt_tasks(rt_se, rt_rq);
> @@ -689,31 +685,33 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
> * followed by enqueue.
> */
> static
> -void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
> +void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
> {
> - struct rt_prio_array *array = &rt_rq->active;
> -
> if (on_rt_rq(rt_se)) {
> - list_del_init(&rt_se->run_list);
> - list_add_tail(&rt_se->run_list,
> - array->queue + rt_se_prio(rt_se));
> + struct rt_prio_array *array = &rt_rq->active;
> + struct list_head *queue = array->queue + rt_se_prio(rt_se);
> +
> + if (head)
> + list_move(&rt_se->run_list, queue);
> + else
> + list_move_tail(&rt_se->run_list, queue);
> }
> }
>
> -static void requeue_task_rt(struct rq *rq, struct task_struct *p)
> +static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
> {
> struct sched_rt_entity *rt_se = &p->rt;
> struct rt_rq *rt_rq;
>
> for_each_sched_rt_entity(rt_se) {
> rt_rq = rt_rq_of_se(rt_se);
> - requeue_rt_entity(rt_rq, rt_se);
> + requeue_rt_entity(rt_rq, rt_se, head);
> }
> }
>
> static void yield_task_rt(struct rq *rq)
> {
> - requeue_task_rt(rq, rq->curr);
> + requeue_task_rt(rq, rq->curr, 0);
> }
>
> #ifdef CONFIG_SMP
> @@ -753,6 +751,30 @@ static int select_task_rq_rt(struct task_struct *p, int sync)
> */
> return task_cpu(p);
> }
> +
> +static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
> +{
> + cpumask_t mask;
> +
> + if (rq->curr->rt.nr_cpus_allowed == 1)
> + return;
> +
> + if (p->rt.nr_cpus_allowed != 1
> + && cpupri_find(&rq->rd->cpupri, p, &mask))
> + return;
> +
> + if (!cpupri_find(&rq->rd->cpupri, rq->curr, &mask))
> + return;
> +
> + /*
> + * There appears to be other cpus that can accept
> + * current and none to run 'p', so lets reschedule
> + * to try and push current away:
> + */
> + requeue_task_rt(rq, p, 1);
> + resched_task(rq->curr);
> +}
> +
> #endif /* CONFIG_SMP */
>
> /*
> @@ -778,18 +800,8 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
> * to move current somewhere else, making room for our non-migratable
> * task.
> */
> - if((p->prio == rq->curr->prio)
> - && p->rt.nr_cpus_allowed == 1
> - && rq->curr->rt.nr_cpus_allowed != 1) {
> - cpumask_t mask;
> -
> - if (cpupri_find(&rq->rd->cpupri, rq->curr, &mask))
> - /*
> - * There appears to be other cpus that can accept
> - * current, so lets reschedule to try and push it away
> - */
> - resched_task(rq->curr);
> - }
> + if (p->prio == rq->curr->prio && !need_resched())
> + check_preempt_equal_prio(rq, p);
> #endif
> }
>
> @@ -1415,7 +1427,7 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
> * on the queue:
> */
> if (p->rt.run_list.prev != p->rt.run_list.next) {
> - requeue_task_rt(rq, p);
> + requeue_task_rt(rq, p, 0);
> set_tsk_need_resched(p);
> }
> }
>
> ---
>
>
> --Dmitry
>
>
>
--
Best regards,
Dmitry Adamushko
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