Bad performance with XFS + 2.6.38 / 2.6.39

[Dave Chinner]

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?
> 
> Maildir++

Which is what?

> >2.  Is the Dovecot rev and config the same everywhere, before/after?
> Yes
> >3.  Are Dovecot instances using NFS to access the XFS volumes?
> NO. direct LVM volumes from SAN
> >4.  Is this a  Dovecot 2.x cluster with director and NFS storage?
> >
> NO. This is dovecot plain & simple.
> 
> When I go back to older kernels, the load go down. With newer
> kernel, all is working well too, but load (as reported by uptime) is
> higher.

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?

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com