Subject: Re: problem with nfs latency during high IO
From: Harshula Jayasuriya <harshula@redhat.com>
To: Chuck Lever <chuck.lever@oracle.com>, Judith Flo Gaya <jflo@imppc.org>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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Date: Thu, 17 Mar 2011 12:21:24 +1100
Message-ID: <1300324884.7042.4.camel@serendib>
Sender: linux-nfs-owner@vger.kernel.org
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Hi Chuck & Judith,

On Tue, 2011-03-15 at 14:15 -0400, Chuck Lever wrote:
> On Mar 15, 2011, at 2:03 PM, Chuck Lever wrote:
> > On Mar 15, 2011, at 1:25 PM, Judith Flo Gaya wrote:

> >> BTW i understand the time issue, but again, if the version of the
> kernel that the red hat has installed allows me to get the information
> soon, why a newer kernel in fedora does not?
> > 
> > Sounds like a bug.  Fedora kernels newer than 2.6.32 should work as
> well as, or better than, RHEL 6.
> 
> Looks like commit acdc53b2 "NFS: Replace __nfs_write_mapping with
> sync_inode()" removes the code that holds i_mutex while trying to
> flush writes before a GETATTR.  This means application writes can
> possibly starve a stat(2) call.  Trond, this seems like a
> regression...?

RHEL 6.0 released with RH kernel 2.6.32-71 and it *does* contain the
commit acdc53b2 "NFS: Replace __nfs_write_mapping with sync_inode()"
backported to 2.6.32. So, I doubt that the reported bad Fedora
performance is due to that commit.

cya,
#