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Re: [Qemu-devel] [5839] qemu-img: open files with cache=writeback
From: |
Aurelien Jarno |
Subject: |
Re: [Qemu-devel] [5839] qemu-img: open files with cache=writeback |
Date: |
Mon, 1 Dec 2008 00:47:06 +0100 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
On Sun, Nov 30, 2008 at 04:56:23PM -0600, Anthony Liguori wrote:
> Aurelien Jarno wrote:
> >Revision: 5839
> > http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5839
> >Author: aurel32
> >Date: 2008-11-30 19:12:49 +0000 (Sun, 30 Nov 2008)
> >
> >Log Message:
> >-----------
> >qemu-img: open files with cache=writeback
> >
> >Data integrity is not important in qemu-img, so open the files with
> >cache=writeback. This fixes the performance regression seen with qemu-img
> >since revision 5485, and most particularly with the qcow2 format.
> >
> >Signed-off-by: Aurelien Jarno <address@hidden>
> >
>
> My thinking was to just make qcow2 always default to cache=writeback. I
> posted an RFC but received no feedback. I guess that means noone
> disagreed :-)
>
Sorry if I haven't answered to your RFC, but as you said no complains
means the patch is ok. I think you can commit it.
I have tried your patch to solve the problem, but it was not fixing all
the problems: other formats are also affected by the slowdown, as the
I/O operations in qemu-img are very different than in qemu.
--
.''`. Aurelien Jarno | GPG: 1024D/F1BCDB73
: :' : Debian developer | Electrical Engineer
`. `' address@hidden | address@hidden
`- people.debian.org/~aurel32 | www.aurel32.net