[Cluster-devel] Re: Why the gfs2 performance regressed?

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

On Mon, 2008-01-07 at 17:48 +0800, rae l wrote:
> On Jan 3, 2008 5:36 PM, Denis Cheng <crquan@gmail.com> wrote:
> > After some bisecting work, now 2.6.22.15 is verified to be able to
> > support samba high performance, while 2.6.23 cannot,
> git bisecting work not finished, now v2.6.22 good and v2.6.23-rc1 bad.
> 
> 2.6.22-g3bd858ab also good.
> 

One of the patches I see in this range is:

commit 60446067ba7a8e890a91db3b4a7436fe0ebd2dee
Author: Marc Eshel <eshel@almaden.ibm.com>
Date:   Mon Jan 15 18:33:36 2007 -0500

    gfs2: stop giving out non-cluster-coherent leases


Now I wonder if samba is using fcntl locks rather than (incorrect, in
the clustered GFS2 case, since it doesn't support them) leases and that
is now why you are seeing the slow down. You could try (for testing
purposes only - don't do this with any important data) setting the
localflocks flag on mount and see if that makes a difference to the
speed.

If it does make a difference, then the problem is just that GFS2 doesn't
support leases in a clustered environment. If it makes no difference,
then it points more towards there being a slow-down in the I/O side,
which seems odd since my general impression is that I/O has been getting
faster recently,

Steve.