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Re: xfs performance problem

To: Martin Steigerwald <Martin@xxxxxxxxxxxx>
Subject: Re: xfs performance problem
From: Benjamin Schindler <bschindler@xxxxxxxxxxx>
Date: Sun, 1 May 2011 18:56:03 +0200
Cc: <xfs@xxxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>
In-reply-to: <201104291828.46420.Martin@xxxxxxxxxxxx>
References: <201104291828.46420.Martin@xxxxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110307 Lightning/1.0b3pre Thunderbird/3.1.9
Hi

On 29.04.2011 18:28, Martin Steigerwald wrote:
> 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?
> 

Well, that doesn't seem to work then may be? As always, I'm willing to
do testing and provide info if required

Cheers
Benjamin

p.s. please keep the cc

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