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Re: Backporting the concurrent direct IO write fix to 3.4

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: Backporting the concurrent direct IO write fix to 3.4
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 4 Jul 2012 09:11:22 +1000
Cc: Kerin Millar <kerframil@xxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20120703160949.GD855@xxxxxxxxxxxxx>
References: <4FF2F41F.5000504@xxxxxxxxx> <20120703160949.GD855@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Tue, Jul 03, 2012 at 12:09:49PM -0400, Christoph Hellwig wrote:
> On Tue, Jul 03, 2012 at 02:31:11PM +0100, Kerin Millar wrote:
> > Hi,
> > 
> > I recently became aware of commit 507630b2 (use shared ilock mode for
> > direct IO writes by default). I understand that this fixes a regression
> > which can have a notable impact upon MySQL performance. This is of
> > considerable interest to myself because my MySQL servers have to contend
> > with a really tough workload.
> > 
> > The patch applies cleanly to 3.4 stable but is it actually safe to use
> > it there? Or does it depend on other changes to XFS, such that I'd be
> > better off holding out for 3.5? Any advice would be greatly appreciated.
> 
> You want the whole series starting at b4d05e3019692fc5a8c573fbce60de2d48c5b7a1
> without the earlier patches there are potential problems when using
> quotas.
> 
> On the one hand I'd love to see these patches go into 3.4-stable as it's
> going to be a long term release,

Is it? So we will have long term support kernels for 3.0.x, 3.2.x
and now 3.4.x? 3.0.x is the long term stable kernel I'm targetting
for backports and there's no way I can really handle more than
that...

> on the other hand they are fairly
> invasive.  If you can give a headsup after passing xfstests and heavy
> mysql testing including benchmarks it might make sense to consider them.

I've got to port them back to 3.0, so I'm not sure it makes
sense to port them to 3.4.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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