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Subject: Re: [RFC][PATCH 3/9] CPU controller - Adds timeslice scaling
From: Mike Galbraith <efault@gmx.de>
To: maeda.naoaki@jp.fujitsu.com
Cc: linux-kernel@vger.kernel.org, ckrm-tech@lists.sourceforge.net
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Date: Fri, 21 Apr 2006 10:17:29 +0200
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On Fri, 2006-04-21 at 11:27 +0900, maeda.naoaki@jp.fujitsu.com wrote:
> Index: linux-2.6.17-rc2/kernel/sched.c
> ===================================================================
> --- linux-2.6.17-rc2.orig/kernel/sched.c
> +++ linux-2.6.17-rc2/kernel/sched.c
> @@ -173,10 +173,17 @@
>  
>  static unsigned int task_timeslice(task_t *p)
>  {
> +	unsigned int timeslice;
> +
>  	if (p->static_prio < NICE_TO_PRIO(0))
> -		return SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio);
> +		timeslice = SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio);
>  	else
> -		return SCALE_PRIO(DEF_TIMESLICE, p->static_prio);
> +		timeslice = SCALE_PRIO(DEF_TIMESLICE, p->static_prio);
> +
> +	if (!TASK_INTERACTIVE(p))
> +		timeslice = cpu_rc_scale_timeslice(p, timeslice);
> +
> +	return timeslice;
>  }

Why does timeslice scaling become undesirable if TASK_INTERACTIVE(p)?
With this barrier, you will completely disable scaling for many loads.

Is it possible you meant !rt_task(p)?

(The only place I can see scaling as having a large effect is on gobs of
non-sleeping tasks.  Slice width doesn't mean much otherwise.)

	-Mike