linux-kernel - Re: Patch "sched: Give CPU bound RT tasks preference" has been added to the 2.6.32-longterm tree

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Message-ID: <1297810967.23343.122.camel@gandalf.stny.rr.com>
Date:	Tue, 15 Feb 2011 18:02:47 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	gregkh@...e.de
Cc:	srostedt <srostedt@...hat.com>, a.p.zijlstra@...llo.nl,
	efault@....de, ghaskins@...ell.com, mingo@...e.hu,
	stable@...nel.org, stable-commits@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Patch "sched: Give CPU bound RT tasks preference" has been
 added to the 2.6.32-longterm tree

[ Added LKML ]

On Tue, 2011-02-15 at 13:17 -0800, gregkh@...e.de wrote:
> This is a note to let you know that I've just added the patch titled
> 
>     sched: Give CPU bound RT tasks preference
> 
> to the 2.6.32-longterm tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/longterm/longterm-queue-2.6.32.git;a=summary
> 
> The filename of the patch is:
>      0006-sched-Give-CPU-bound-RT-tasks-preference.patch
> and it can be found in the queue-2.6.32 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the 2.6.32 longterm tree,
> please let <stable@...nel.org> know about it.
> 
> 

I don't mind this patch being added to the long term tree. But I'm
curious about what is the criteria for adding changes to it? This is a
performance improvement and not a critical bug fix.

-- Steve

> >From 10db390cadda977081a7a34f60b8ce62557521c9 Mon Sep 17 00:00:00 2001
> From: stable-bot for Steven Rostedt <srostedt@...hat.com>
> Date: Thu, 10 Feb 2011 10:21:08 +0100
> Subject: sched: Give CPU bound RT tasks preference
> 
> From:: Steven Rostedt <srostedt@...hat.com>
> 
> Commit: b3bc211cfe7d5fe94b310480d78e00bea96fbf2a upstream
> 
> If a high priority task is waking up on a CPU that is running a
> lower priority task that is bound to a CPU, see if we can move the
> high RT task to another CPU first. Note, if all other CPUs are
> running higher priority tasks than the CPU bounded current task,
> then it will be preempted regardless.
> 
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Gregory Haskins <ghaskins@...ell.com>
> LKML-Reference: <20100921024138.888922071@...dmis.org>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> Signed-off-by: Mike Galbraith <efault@....de>
> Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> ---
>  kernel/sched_rt.c |    8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> --- a/kernel/sched_rt.c
> +++ b/kernel/sched_rt.c
> @@ -965,7 +965,8 @@ select_task_rq_rt(struct rq *rq, struct
>  	 * For equal prio tasks, we just let the scheduler sort it out.
>  	 */
>  	if (unlikely(rt_task(rq->curr)) &&
> -	    rq->curr->prio < p->prio &&
> +	    (rq->curr->rt.nr_cpus_allowed < 2 ||
> +	     rq->curr->prio < p->prio) &&
>  	    (p->rt.nr_cpus_allowed > 1)) {
>  		int cpu = find_lowest_rq(p);
>  
> @@ -1493,9 +1494,10 @@ static void task_woken_rt(struct rq *rq,
>  	if (!task_running(rq, p) &&
>  	    !test_tsk_need_resched(rq->curr) &&
>  	    has_pushable_tasks(rq) &&
> +	    p->rt.nr_cpus_allowed > 1 &&
>  	    rt_task(rq->curr) &&
> -	    rq->curr->prio < p->prio &&
> -	    p->rt.nr_cpus_allowed > 1)
> +	    (rq->curr->rt.nr_cpus_allowed < 2 ||
> +	     rq->curr->prio < p->prio))
>  		push_rt_tasks(rq);
>  }
>  
> 
> 
> Patches currently in longterm-queue-2.6.32 which might be from srostedt@...hat.com are


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