From: Bartlomiej ZOLNIERKIEWICZ <Bartlomiej.Zolnierkiewicz@cern.ch>
To: Andreas Hirstius <Andreas.Hirstius@cern.ch>
Cc: Gelato technical <gelato-technical@gelato.unsw.edu.au>,
linux-kernel@vger.kernel.org
Subject: Re: Serious performance degradation on a RAID with kernel 2.6.10-bk7 and later
Date: Thu, 21 Apr 2005 11:42:31 +0200 [thread overview]
Message-ID: <42677587.8030707@cern.ch> (raw)
In-Reply-To: <58cb370e05042102272ce70f2@mail.gmail.com>
Hi!
> A small update.
>
> Patching mm/filemap.c is not necessary in order to get the improved
> performance!
> It's sufficient to remove roundup_pow_of_two from |get_init_ra_size ...
>
> So a simple one-liner changes to picture dramatically.
> But why ?!?!?
roundup_pow_of_two() uses fls() and ia64 has buggy fls() implementation
[ seems that David fixed it but patch is not in the mainline yet]:
http://www.mail-archive.com/linux-ia64@vger.kernel.org/msg01196.html
That would also explain why you couldn't reproduce the problem on ia32
Xeon machines.
Bartlomiej
next prev parent reply other threads:[~2005-04-21 9:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-20 17:37 Serious performance degradation on a RAID with kernel 2.6.10-bk7 and later Andreas Hirstius
2005-04-20 16:55 ` jmerkey
2005-04-20 18:04 ` Andreas Hirstius
2005-04-20 18:24 ` Andreas Hirstius
2005-04-20 19:17 ` jmerkey
2005-04-21 1:11 ` Nick Piggin
2005-04-21 8:32 ` Andreas Hirstius
[not found] ` <58cb370e05042102272ce70f2@mail.gmail.com>
2005-04-21 9:42 ` Bartlomiej ZOLNIERKIEWICZ [this message]
2005-04-21 11:30 ` Andreas Hirstius
2005-04-21 15:05 ` [Gelato-technical] " David Mosberger
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