linux-kernel - Re: [ANNOUNCE] Native Linux KVM tool v2

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Message-Id: <7A30A509-47AA-4E72-ABF3-937005900F9D@suse.de>
Date:	Thu, 16 Jun 2011 00:07:09 +0200
From:	Alexander Graf <agraf@...e.de>
To:	Anthony Liguori <anthony@...emonkey.ws>
Cc:	Prasad Joshi <prasadjoshi124@...il.com>,
	Pekka Enberg <penberg@...nel.org>, Avi Kivity <avi@...hat.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Sasha Levin <levinsasha928@...il.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Asias He <asias.hejun@...il.com>,
	Jens Axboe <jaxboe@...ionio.com>
Subject: Re: [ANNOUNCE] Native Linux KVM tool v2


On 16.06.2011, at 00:04, Anthony Liguori wrote:

> On 06/15/2011 03:13 PM, Prasad Joshi wrote:
>> On Wed, Jun 15, 2011 at 6:10 PM, Pekka Enberg<penberg@...nel.org>  wrote:
>>> On Wed, Jun 15, 2011 at 7:30 PM, Avi Kivity<avi@...hat.com>  wrote:
>>>> On 06/15/2011 06:53 PM, Pekka Enberg wrote:
>>>>> 
>>>>> - Fast QCOW2 image read-write support beating Qemu in fio benchmarks. See
>>>>> the
>>>>>   following URL for test result details: https://gist.github.com/1026888
>>>> 
>>>> This is surprising.  How is qemu invoked?
>>> 
>>> Prasad will have the details. Please note that the above are with Qemu
>>> defaults which doesn't use virtio. The results with virtio are little
>>> better but still in favor of tools/kvm.
>>> 
>> 
>> The qcow2 image used for testing was copied on to /dev/shm to avoid
>> the disk delays in performance measurement.
>> 
>> QEMU was invoked with following parameters
>> 
>> $ qemu-system-x86_64 -hda<disk image on hard disk>  -hdb
>> /dev/shm/test.qcow2 -m 1024M
> 
> Looking more closely at native KVM tools, you would need to use the following invocation to have an apples-to-apples comparison:
> 
> qemu-system-x86_64 -drive file=/dev/shm/test.qcow2,cache=writeback,if=virtio

Wouldn't this still be using threaded AIO mode? I thought KVM tools used native AIO?


Alex

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