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Date: Tue, 30 Dec 2003 05:27:04 -0500 (EST)
From: Thomas Molina <tmolina@cablespeed.com>
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To: William Lee Irwin III <wli@holomorphy.com>
cc: Martin Schlemmer <azarah@nosferatu.za.org>,
       Linus Torvalds <torvalds@osdl.org>,
       Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: 2.6.0 performance problems
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On Mon, 29 Dec 2003, William Lee Irwin III wrote:

> On Tue, 2003-12-30 at 00:58, Thomas Molina wrote:
> >> It certainly looks like DMA is enabled.  Under 2.4 I get:
> >> [root@lap root]# hdparm /dev/hda
> [...]
> >>  readahead    =  8 (on)
> [...]
> >> Under 2.6  I get:
> >> [root@lap root]# hdparm /dev/hda
> [...]
> >>  readahead    = 256 (on)
> 
> On Tue, Dec 30, 2003 at 01:14:45AM +0200, Martin Schlemmer wrote:
> > Increase your readahead:
> >  # hdparm -a 8192 /dev/hda
> > BTW:  As we really do get this question a _lot_ of times, why
> >       don't the ide layer automatically set a higher readahead
> >       if there is enough cache on the drive or something?
> 
> Could you try lowering 2.6's readahead to 2.4's levels in order to rule
> out readahead-induced thrashing?

I thought I had already sent that.  The timings for readahead of 8 was:

real    25m39.653s
user    0m37.594s
sys     0m55.454s

Increasing readahead in 2.6 to 8192 likewise doesn't help.