Re: Bad performance with XFS + 2.6.38 / 2.6.39

From: Stan Hoeppner <stan@hardwarefreak.com>
To: Yann Dupont <Yann.Dupont@univ-nantes.fr>
Cc: xfs@oss.sgi.com
Subject: Re: Bad performance with XFS + 2.6.38 / 2.6.39
Date: Wed, 21 Dec 2011 09:10:21 -0600	[thread overview]
Message-ID: <4EF1F6DD.8020603@hardwarefreak.com> (raw)
In-Reply-To: <4EF1A224.2070508@univ-nantes.fr>

On 12/21/2011 3:08 AM, Yann Dupont wrote:
> Le 12/12/2011 03:00, Xupeng Yun a écrit :
>>
>>
>> On Mon, Dec 12, 2011 at 09:00, Dave Chinner <david@fromorbit.com
>> <mailto:david@fromorbit.com>> wrote:
>>
>>     Oh, of course, now I remember what the problem is - it's a locking
>>     issue that was fixed in 3.0.11, 3.1.5 and 3.2-rc1.
>>
>>
>> Got it, thanks.
>>
>> -- 
>> Xupeng Yun
>> http://about.me/xupeng
>>
>>
>> _______________________________________________
>> xfs mailing list
>> xfs@oss.sgi.com
>> http://oss.sgi.com/mailman/listinfo/xfs
> 
> I'm seeing more or less the same here.
> 
> Generally speaking XFS code in recent kernels seems to decrease CPU
> usage and be faster, which is a very good thing (good works, guy). But...
> 
> On two particular server, with recent kernels, I experience a much
> higher load than expected, but it's very hard to tell what's wrong. The
> system seems more in I/O wait. Older kernels (2.6.32.xx and 2.6.26.xx)
> gives better results.
> 
> Following this thread, I thought I have the same problems, but it's
> probably not the case, as I have tested 2.6.38.xx, 3.0.13, 3.1.5 with
> same results.
> 
> Thoses servers are mail (dovecot) servers, with lots of simultaneous
> imap clients (5000+) an lots of simultaneous message delivery.
> 
> These are linux-vservers, on top of LVM volumes. The storage is SAN with
> 15k RPM SAS drives (and battery backup).
> 
> I know barriers were disabled in older kernels, so with recents kernels,
> XFS volumes were mounted with nobarrier.
> 
> As those servers are critical for us, I can't really test, hardly give
> you more precise numbers, and I don't know how to accurately reproduce
> this platform to test what's wrong. I know this is NOT a precise bug
> report and it won't help much.
> 
> All I can say IS :
> 
> - read operations seems no slower with recent kernels, backups take
> approximatively the same time ;
> - I'd say (but I have no proof) that delivery of new mails takes more
> time and is more synchronous than before, like nobarrier have no effect.
> 
> Does this ring a bell to some of you ?

1.  What mailbox format are you using?  Is this a constant or variable?
2.  Is the Dovecot rev and config the same everywhere, before/after?
3.  Are Dovecot instances using NFS to access the XFS volumes?
4.  Is this a  Dovecot 2.x cluster with director and NFS storage?

-- 
Stan

_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs