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Re: Bad performance with XFS + 2.6.38 / 2.6.39

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: Bad performance with XFS + 2.6.38 / 2.6.39
From: Yann Dupont <Yann.Dupont@xxxxxxxxxxxxxx>
Date: Thu, 22 Dec 2011 10:23:14 +0100
Cc: stan@xxxxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <20111221222623.GF23662@dastard>
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Le 21/12/2011 23:26, Dave Chinner a écrit :
On Wed, Dec 21, 2011 at 06:56:34PM +0100, Yann Dupont wrote:
Le 21/12/2011 16:10, Stan Hoeppner a écrit :

1.  What mailbox format are you using?  Is this a constant or variable?


Which is what?

Each message is saved as an individual files. With loaded mailboxex, you can end with thousands of files under one directory.

Can you run a block trace on both kernels (for say five minutes)
when the load differential is showing up and provide that to us so
we can see how the IO patterns are differing?

Yes. Keep in mind that I can have very different load in 5 minutes distance.
I have 2 options here :

Case 1 : For server 1, running with kernel 2.6.26, blktrace it, reboot in 3.1.5, blktrace it. OR

Case 2 : Server 1 running 2.6.26 and Server 2 running 3.1.5

in Case 1 you have the same set of users and the same config garantied.

in case 2, you don't have the same set of users, but the load can be quite symetric (think of mailing list)

I will go for case 2 I think.

Last question :

The volumes are on top of lvm2 (sitting on top of multipath dm)

I'll try to blktrace the volume itself, but I can end blktracing the scsi primary path (don't know if it make a difference)

Is there any option you want in blktrace ???


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

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