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Re: Bad performance with XFS + 2.6.38 / 2.6.39

To: xfs@xxxxxxxxxxx
Subject: Re: Bad performance with XFS + 2.6.38 / 2.6.39
From: Yann Dupont <Yann.Dupont@xxxxxxxxxxxxxx>
Date: Wed, 21 Dec 2011 10:08:52 +0100
In-reply-to: <CACaf2ab-YjXAFm767MmRU5iuOmvkqQW3ZTfQewD5SGvF-opgYQ@xxxxxxxxxxxxxx>
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Le 12/12/2011 03:00, Xupeng Yun a écrit :

On Mon, Dec 12, 2011 at 09:00, Dave Chinner <david@xxxxxxxxxxxxx
<mailto:david@xxxxxxxxxxxxx>> 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

xfs mailing list

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 ?

Yann Dupont - Service IRTS, DSI Université de Nantes
Tel : - Mail/Jabber : Yann.Dupont@xxxxxxxxxxxxxx

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