From: Chris Mason <chris.mason@oracle.com>
To: Avi Kivity <avi@redhat.com>
Cc: Diego Calleja <diegocg@gmail.com>, linux-btrfs@vger.kernel.org
Subject: Re: Poor performance with qemu
Date: Thu, 8 Apr 2010 11:32:13 -0400 [thread overview]
Message-ID: <20100408153213.GJ1400@think> (raw)
In-Reply-To: <4BBDF636.5010002@redhat.com>
On Thu, Apr 08, 2010 at 06:28:54PM +0300, Avi Kivity wrote:
> On 04/08/2010 06:26 PM, Chris Mason wrote:
> >>
> >>>Once the O_DIRECT read patch is in, you can switch to that, or tell qemu
> >>>to use a writeback cache instead.
> >>Even with writeback qemu will issue a lot of fsyncs.
> >Oh, I didn't see that when I was testing, when does it fsync?
>
> When it updates qcow2 metadata or when the guest issues a barrier.
> It's relatively new. I have a patch that introduces cache=volatile
> somewhere.
Ok, that's actually perfect. I'll retest with that if I can get
qemu-git to work here.
-chris
next prev parent reply other threads:[~2010-04-08 15:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-28 15:18 Poor performance with qemu Diego Calleja
2010-03-30 12:56 ` Chris Mason
2010-04-08 14:58 ` Avi Kivity
2010-04-08 15:21 ` Gordan Bobic
2010-04-08 15:26 ` Chris Mason
2010-04-08 15:28 ` Avi Kivity
2010-04-08 15:32 ` Chris Mason [this message]
2010-04-08 15:34 ` Christoph Hellwig
2010-04-08 15:36 ` Avi Kivity
2010-04-08 15:39 ` Christoph Hellwig
2010-04-08 15:32 ` Christoph Hellwig
-- strict thread matches above, loose matches on Subject: below --
2010-03-29 19:21 Markus Suvanto
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