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Date: Thu, 16 Jun 2011 08:42:48 +0300
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Subject: Re: [ANNOUNCE] Native Linux KVM tool v2
From: Pekka Enberg <penberg@kernel.org>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Prasad Joshi <prasadjoshi124@gmail.com>, Avi Kivity <avi@redhat.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@elte.hu>, Sasha Levin <levinsasha928@gmail.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>, Asias He <asias.hejun@gmail.com>,
        Jens Axboe <jaxboe@fusionio.com>,
        Anthony Liguori <anthony@codemonkey.ws>
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On Thu, Jun 16, 2011 at 8:29 AM, Stefan Hajnoczi <stefanha@gmail.com> wrote:
> On Wed, Jun 15, 2011 at 11:04 PM, Anthony Liguori <anthony@codemonkey.ws> wrote:
>> On 06/15/2011 03:13 PM, Prasad Joshi wrote:
>>>
>>> On Wed, Jun 15, 2011 at 6:10 PM, Pekka Enberg<penberg@kernel.org>  wrote:
>>>>
>>>> On Wed, Jun 15, 2011 at 7:30 PM, Avi Kivity<avi@redhat.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
>
> In addition to this it is important to set identical guest RAM sizes
> (QEMU's -m <ram_mb>) option.

Right.

> If you are comparing with qemu.git rather than qemu-kvm.git then you
> need to ./configure --enable-io-thread and launch with QEMU's
> -enable-kvm option.

I think Prasad is testing qemu-kvm.git.