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Date: Wed, 05 Dec 2001 12:13:34 -0800
From: Andrew Morton <akpm@zip.com.au>
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To: Roy Sigurd Karlsbakk <roy@karlsbakk.net>
CC: linux-kernel@vger.kernel.org
Subject: Re: /proc/sys/vm/(max|min)-readahead effect????
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Roy Sigurd Karlsbakk wrote:
> 
> hi all
> 
> I've just upgraded to 2.4.16 to get /proc/sys/vm/(max|min)-readahead
> available. I've got this idea...
> 
> If lots of files (some hundered) are read simultaously, I waste all the
> i/o time in seeks. However, if I increase the readahead, it'll read more
> data at a time, and end up with seeking a lot less.
> 
> The harddrive I'm testing this with, is a cheap 20G IDE drive.

/proc/sys/vm/*-readhead is a no-op for IDE.  It doesn't do
anything.   You must use

	echo file_readahead:100 > /proc/ide/ide0/hda/settings

to set the readhead to 100 pages (409600 bytes).

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