Re: How to track down abysmal performance ata - raid1 - crypto - vg/lv - xfs

[Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>]

Christoph,

On Wed, Aug 04, 2010 at 04:50:39AM -0400, Christoph Hellwig wrote:
> On Wed, Aug 04, 2010 at 09:35:46AM +0200, Dominik Brodowski wrote:
> > How can I best track down the cause of the performance problem, 
> > a) without rebooting too often, and
> > b) without breaking up the setup specified above (production system)?
> 
> So did you just upgrade the system from an earlier kernel that did not
> show these problems?

No, 2.6.31 to 2.6.34 show similar behaviour.

>  Or did no one notice them before?

Well, there are some reports relating to XFS on MD or RAID, though I couldn't
find a resolution to the issues reported, e.g.

- http://kerneltrap.org/mailarchive/linux-raid/2009/10/12/6490333
- http://lkml.indiana.edu/hypermail/linux/kernel/1006.1/00099.html

However, I think we can rule out barriers, as XFS is mounted "nobarrier"
here.

Best,
        Dominik