Re: [Qemu-devel] [5839] qemu-img: open files with cache=writeback

[Aurelien Jarno <aurelien@aurel32.net>]

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 <aurelien@aurel32.net>
> >  
> 
> 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.

-- 
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