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

From: Kevin Wolf <kwolf@redhat.com>
To: Yehuda Sadeh Weinraub <yehudasa@gmail.com>
Cc: Sage Weil <sage@newdream.net>,
	qemu-devel@nongnu.org, ceph-devel@vger.kernel.org
Subject: Re: [Qemu-devel] [PATCH 0/2] improve qemu-img conversion performance
Date: Mon, 12 Sep 2011 10:05:05 +0200	[thread overview]
Message-ID: <4E6DBD31.5050702@redhat.com> (raw)
In-Reply-To: <CAC-hyiHKmD9_z69XxRUE_3iZ--Vnb+q2B8kwQ985PHZP_2_jZA@mail.gmail.com>

Am 12.09.2011 05:17, schrieb Yehuda Sadeh Weinraub:
> On Sun, Sep 11, 2011 at 8:14 PM, Sage Weil <sage@newdream.net> 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.

Yes, I agree that the change makes sense anyway.

Kevin