linux-kernel - Re: [PATCH v2 2/3] sched/dl: Cleanup prio_changed

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Date:	Tue, 21 Oct 2014 20:33:44 +0400
From:	Kirill Tkhai <ktkhai@...allels.com>
To:	Juri Lelli <juri.lelli@....com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Kirill Tkhai <tkhai@...dex.ru>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...il.com>
Subject: Re: [PATCH v2 2/3] sched/dl: Cleanup prio_changed_dl()

В Вт, 21/10/2014 в 17:24 +0100, Juri Lelli пишет:
> Hi Kirill,
> 
> On 02/10/14 10:52, Kirill Tkhai wrote:
> > В Чт, 02/10/2014 в 11:36 +0200, Peter Zijlstra пишет:
> >> On Wed, Oct 01, 2014 at 01:04:35AM +0400, Kirill Tkhai wrote:
> >>> From: Kirill Tkhai <ktkhai@...allels.com>
> >>>
> >>> rq->curr task can't be in "dequeued" state in prio_changed_dl().
> >>> (The only place we can have that is __schedule()). So, we delete
> >>> rq->curr check.
> >>
> >> the CBS timer can throttle it right?
> > 
> > Yeah, it's better to check for on_dl_rq():
> > 
> > [PATCH]sched/dl: Cleanup prio_changed_dl()
> >     
> > rq->curr task can't be in "dequeued" state in prio_changed_dl().
> > (The only place we can have that is __schedule()). So, we delete
> > rq->curr check.
> > 
> > We shouldn't do balancing if deadline task is throttled too.
> > 
> > Also delete "else" branch which is dead code (switched_to_dl()
> > is not interested in dequeued tasks and we are not interested
> > in balancing in this case).
> > 
> 
> So, I agree that calling switched_to_dl() makes little sense,
> but don't we have to deal with updates to not running tasks as
> in rt.c? Something like this maybe?

Looks good. No objections from me.

> 
> From 75ee75a5fd76526baaed3ba8a58f3ff7daa89cd6 Mon Sep 17 00:00:00 2001
> From: Juri Lelli <juri.lelli@....com>
> Date: Tue, 21 Oct 2014 17:15:15 +0100
> Subject: [PATCH] sched/deadline: cleanup prio_changed_dl()
> 
> ---
>  kernel/sched/deadline.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 28d6088..1e62e31 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1661,7 +1661,10 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
>  static void prio_changed_dl(struct rq *rq, struct task_struct *p,
>  			    int oldprio)
>  {
> -	if (task_on_rq_queued(p) || rq->curr == p) {
> +	if (!on_dl_rq(&p->dl))
> +		return;
> +
> +	if (rq->curr == p) {
>  #ifdef CONFIG_SMP
>  		/*
>  		 * This might be too much, but unfortunately
> @@ -1688,8 +1691,15 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
>  		 */
>  		resched_curr(rq);
>  #endif /* CONFIG_SMP */
> -	} else
> -		switched_to_dl(rq, p);
> +	} else {
> +		/*
> +		 * This task is not running, so if its deadline is
> +		 * now more imminent than that of the current running
> +		 * task then reschedule.
> +		 */
> +		if (dl_time_before(p->dl.deadline, rq->curr->dl.deadline))
> +			resched_curr(rq);
> +	}
>  }
>  
>  const struct sched_class dl_sched_class = {


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