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From: Andreas Hirstius <Andreas.Hirstius@cern.ch>
To: Bartlomiej ZOLNIERKIEWICZ <Bartlomiej.Zolnierkiewicz@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 13:30:50 +0200	[thread overview]
Message-ID: <42678EEA.6070109@cern.ch> (raw)
In-Reply-To: <42677587.8030707@cern.ch>

Hi,

The fls() patch from David solves the problem :-))

Do you have an idea, when it will be in the mainline kernel??

Andreas



Bartlomiej ZOLNIERKIEWICZ wrote:

>
> 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
>

  reply	other threads:[~2005-04-21 11:31 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
2005-04-21 11:30         ` Andreas Hirstius [this message]
2005-04-21 15:05           ` [Gelato-technical] " David Mosberger

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