Re: [Qemu-devel] [PATCH 0/2] improve qemu-img conversion performance

[Yehuda Sadeh Weinraub]

On Sun, Sep 11, 2011 at 8:14 PM, Sage Weil <address@hidden> wrote:
> On Fri, 9 Sep 2011, Kevin Wolf wrote:
>> Am 08.09.2011 18:36, schrieb Sage Weil:
>> > On Thu, 8 Sep 2011, Kevin Wolf wrote:
>> >> Am 08.09.2011 01:06, schrieb Yehuda Sadeh:
>> >>> The following set of patches improve the qemu-img conversion process
>> >>> performance. When using a higher latency backend, small writes have a
>> >>> severe impact on the time it takes to do image conversion.
>> >>> We switch to using async writes, and we avoid splitting writes due to
>> >>> holes when the holes are small enough.
>> >>>
>> >>> Yehuda Sadeh (2):
>> >>>   qemu-img: async write to block device when converting image
>> >>>   qemu-img: don't skip writing small holes
>> >>>
>> >>>  qemu-img.c |   34 +++++++++++++++++++++++++++-------
>> >>>  1 files changed, 27 insertions(+), 7 deletions(-)
>> >>>
>> >>
>> >> This doesn't seem to be against git master or the block tree. Please 
>> >> rebase.
>> >>
>> >> I think that commit a22f123c may obsolete your patch 2/2.
>> >
>> > With git.kernel.org down, where should I be looking for the latest
>> > upstream?
>>
>> qemu has never been on kernel.org. The interesting repositories for you are:
>>
>> * Upstream: git://git.qemu.org/qemu.git master
>> * Block development branch: git://repo.or.cz/qemu/kevin.git block
>
> Oh right.  I've been working from qemu-kvm.git.
>
> I've done some (still minimal) testing, and it looks like the combination
> of a22f123c and the new writeback/flush stuff in librbd gets the same
> result as doing async io explicitly from qemu-img.c.  Want to take a look,
> Yehuda?  It still defaults to off, so you'll need to add
> rbd_writeback_window=8000000 or similar to the rbd device string.
>

I'll take a look. I do have a rebased version for the qemu-img async
patch, and I think qemu can benefit from that anyway.

Yehuda