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Date: Thu, 16 Jun 2011 06:29:05 +0100
Message-ID: <BANLkTimmnUAywjHbkSoepBdyCHPHy-B3pw@mail.gmail.com>
Subject: Re: [ANNOUNCE] Native Linux KVM tool v2
From: Stefan Hajnoczi <stefanha@gmail.com>
To: Prasad Joshi <prasadjoshi124@gmail.com>
Cc: Pekka Enberg <penberg@kernel.org>, 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 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.

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.

Stefan
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