From: Paolo Ornati <ornati@lycos.it>
To: Ed Sweetman <ed.sweetman@wmich.edu>
Subject: Re: Strange IDE performance change in 2.6.1-rc1 (again)
Date: Sat, 10 Jan 2004 18:29:13 +0100
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Cc: Ram Pai <linuxram@us.ibm.com>, Andrew Morton <akpm@osdl.org>,
       gandalf@wlug.westbo.se, linux-kernel@vger.kernel.org
References: <200401021658.41384.ornati@lycos.it> <200401101548.33458.ornati@lycos.it> <40002196.4030506@wmich.edu>
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On Saturday 10 January 2004 17:00, Ed Sweetman wrote:
>
> I'm using 2.6.0-mm1 and i see no difference from setting readahead to
> anything on my extent enabled partitions. So it appears that filesystem
> plays a big part in your numbers here, not just hdd attributes or
> settings.
>
> The partition FILE is on is an ext3 + extents enabled partition. Despite
> not having fadvise (what is this anyway?) the numbers are all real and
> no error occured. Extents totally rocks for this type of data access, as
> you can see below.
>
> Stick to non-fs tests if you want to benchmark fs independent code. Not
> everyone is going to be able to come up with the same results as you and
> as such a possible fix could actually be detrimental, and we'd be stuck
> in a loop of "ide regression" mails.

To run correctly my script you _MUST_ have "fadvise" tool (my script assumes 
it is installed in current directory).

This is what Andrew said:
_____________________________________________________________________
You'll need to unmount and remount the fs in between to remove the file
from pagecache.  Or use fadvise() to remove the pagecache.  There's a
little tool which does that in 

http://www.zip.com.au/~akpm/linux/patches/stuff/ext3-tools.tar.gz
_____________________________________________________________________

so "fadvise" is a simple tool that calls "fadvise64" system call.
This system call lets you do some useful things: for example you can discard 
all the cached pages for a file, that is what my command does.

-- 
	Paolo Ornati
	Linux v2.4.24


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