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Re: xfs performance problem

To: xfs@xxxxxxxxxxx, Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: xfs performance problem
From: Martin Steigerwald <Martin@xxxxxxxxxxxx>
Date: Fri, 29 Apr 2011 18:28:45 +0200
Cc: Benjamin Schindler <bschindler@xxxxxxxxxxx>
sorry, forgot to cc.

Am Mittwoch, 27. April 2011 schrieb Dave Chinner:
> On Tue, Apr 26, 2011 at 09:44:04PM +0200, Benjamin Schindler wrote:
> > Hi
> > 
> > Since upgrading to newer kernels I have serious problems with xfs
> > performance on my root fs.
> > It runs on a software raid 0 with 2 disks. On the same two disks,
> > there are two more partitions running a software raid-1 with ext3.
> > On the ext3 system, I have no issue, so I assume the drives are
> > fine.
> > But on the xfs filesystem, extracting a linux kernel archive takes 5
> > minutes or more, running ldconfig similarily long. The harddrives are
> > sata-2.
> > I'm running gentoo linux with kernel 2.6.38-gentoo-r1. I'm attaching
> > the kernel config but I guess more info is needed - just let me know
> > what is needed.
> 
> more than likely your problem is that barriers have been enabled for
> MD/DM devices on the new kernel, and they aren't on the old kernel.
> XFS uses barriers by default, ext3 does not. Hence XFS performance
> will change while ext3 will not. Check dmesg output when mounting
> the filesystems on the different kernels.

But didn't 2.6.38 replace barriers by explicit flushes the filesystem has to 
wait for - mitigating most of the performance problems with barriers?

-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7

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