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

[Yehuda Sadeh Weinraub]

On Sun, Sep 11, 2011 at 8:17 PM, Yehuda Sadeh Weinraub
<address@hidden> wrote:
> 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.
>
I tested latest librbd with 8k rbd_writeback_window against Kevin's
block branch and it seems that the conversion performance surpasses
what I had seen with my qemu-img changes.

Yehuda