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Date: Thu, 06 Dec 2001 11:09:27 +0100
From: Martin Dalecki <dalecki@evision-ventures.com>
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To: Roy Sigurd Karlsbakk <roy@karlsbakk.net>
CC: Rik van Riel <riel@conectiva.com.br>,
        Marcelo Tosatti <marcelo@conectiva.com.br>,
        linux-kernel@vger.kernel.org
Subject: Re: /proc/sys/vm/(max|min)-readahead effect????
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Roy Sigurd Karlsbakk wrote:
> 
> > I suspect the per-device readahead for IDE is limiting the
> > effect of vm_max_readahead ...
> 
> hm...
> 
> any way to avoid this? I mean... The readahead in vm is layered above the
> actual device, and should therefore not be limited... Am I right? You
> could do several device calls, and fake readahead, and probably get pretty
> much out of it.

He means the hardware device read ahead, which can be changed by using
hdparm -a 32 -A1 /dev/hda
for example.
The value of the read ahead one layer on top of it
(read_ahead array) can't have *any* impact on performance.
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