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Date: Tue, 4 May 2004 12:48:00 -0700
From: Andrew Morton <akpm@osdl.org>
To: Ram Pai <linuxram@us.ibm.com>
Cc: nickpiggin@yahoo.com.au, peter@mysql.com, alexeyk@mysql.com,
       linux-kernel@vger.kernel.org, axboe@suse.de
Subject: Re: Random file I/O regressions in 2.6
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Ram Pai <linuxram@us.ibm.com> wrote:
>
> I ran the following command:
> 
>  /root/sysbench-0.2.5/sysbench/sysbench --num-threads=256 --test=fileio
>  --file-total-size=2800M --file-test-mode=rndrw run 
> 

Alexey and I have been using 16 threads.

You don't tell us how much memory your lab machine has.  The above command
only makes sense if it is less than 400 megabytes.  Otherwise many or all
of the reads are satisfied from pagecache.

I've been testing with mem=256M, --file-total-size=2G.