linux-kernel - Re: [PATCH 2/2] sched/rt: Optimizate task_woken

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Message-ID: <20150430130143.46bd8d43@gandalf.local.home>
Date:	Thu, 30 Apr 2015 13:01:43 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Xunlei Pang <xlpang@....com>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Xunlei Pang <pang.xunlei@...aro.org>
Subject: Re: [PATCH 2/2] sched/rt: Optimizate task_woken_rt()

On Fri,  1 May 2015 00:33:18 +0800
Xunlei Pang <xlpang@....com> wrote:

> From: Xunlei Pang <pang.xunlei@...aro.org>
> 
> - Remove "has_pushable_tasks(rq)" condition, because for queued p,
> "!task_running(rq, p)" and "p->nr_cpus_allowed > 1" implies true
> "has_pushable_tasks(rq)".

This makes sense.

> 
> - Remove "!test_tsk_need_resched(rq->curr)" condition, because
> the flag might be set right before the waking up, but we still
> need to push equal or lower priority tasks, it should be removed.
> Without this condition, we actually get the right logic.

But doesn't that happen when we schedule?

-- Steve

> 
> Signed-off-by: Xunlei Pang <pang.xunlei@...aro.org>
> ---
>  kernel/sched/rt.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index a9d33a3..9d735da 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -2233,8 +2233,6 @@ out:
>  static void task_woken_rt(struct rq *rq, struct task_struct *p)
>  {
>  	if (!task_running(rq, p) &&
> -	    !test_tsk_need_resched(rq->curr) &&
> -	    has_pushable_tasks(rq) &&
>  	    p->nr_cpus_allowed > 1 &&
>  	    (dl_task(rq->curr) || rt_task(rq->curr)) &&
>  	    (rq->curr->nr_cpus_allowed < 2 ||

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