Subject: Re: [PATCH 07/23] readahead: insert cond_resched() calls
From: Lee Revell <rlrevell@joe-job.com>
To: Wu Fengguang <wfg@mail.ustc.edu.cn>
Cc: Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org,
       Con Kolivas <kernel@kolivas.org>
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Date: Sat, 18 Mar 2006 22:50:42 -0500
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On Sun, 2006-03-19 at 10:34 +0800, Wu Fengguang wrote:
> plain text document attachment
> (readahead-insert-cond_resched-calls.patch)
> Since the VM_MAX_READAHEAD is greatly enlarged and the algorithm become more
> complex, it becomes necessary to insert some cond_resched() calls in the
> read-ahead path.
> 
> If desktop users still feel audio jitters with the new read-ahead code,
> please try one of the following ways to get rid of it:
> 
> 1) compile kernel with CONFIG_PREEMPT_VOLUNTARY/CONFIG_PREEMPT
> 2) reduce the read-ahead request size by running
> 	blockdev --setra 256 /dev/hda # or whatever device you are using

Do you have any numbers on this (say, from Ingo's latency tracer)?  Have
you confirmed it's not a latency regression with the default settings?

Lee

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