Subject: Re: Regression seen for patch "sched:dont decrease idle sleep avg"
From: Mike Galbraith <efault@gmx.de>
To: Con Kolivas <kernel@kolivas.org>
Cc: tim.c.chen@linux.intel.com, "Chen, Kenneth W" <kenneth.w.chen@intel.com>,
       linux-kernel@vger.kernel.org, mingo@elte.hu,
       Andrew Morton <akpm@osdl.org>
In-Reply-To: <200605171823.24476.kernel@kolivas.org>
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	 <200605171823.24476.kernel@kolivas.org>
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Date: Wed, 17 May 2006 11:49:23 +0200
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On Wed, 2006-05-17 at 18:23 +1000, Con Kolivas wrote:

> There is a ceiling to the priority beyond which tasks that only ever sleep
> for very long periods cannot surpass.

(Hmm.  The intent is more clear, ie reserve the top for low latency
tasks,... but that sounds a bit like xmms protection.) 

The main problem I see with this ceiling, solely from the interactivity
viewpoint, is that interactive tasks which have started burning cpu
and/or freshly forked interactive tasks land in the same spot.  Thud.c
demonstrates this problem quite well.  You don't want a few copies of
thud in the same queue with your interactive task, much less above it if
it's used enough cpu to drop a notch or two.  Much pain ensues.

	-Mike

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