Re: [ANNOUNCE] Native Linux KVM tool v2

From: Stefan Hajnoczi
Date: Thu Jun 16 2011 - 01:29:18 EST

On Wed, Jun 15, 2011 at 11:04 PM, Anthony Liguori <anthony@xxxxxxxxxxxxx> wrote:
> On 06/15/2011 03:13 PM, Prasad Joshi wrote:
>> On Wed, Jun 15, 2011 at 6:10 PM, Pekka Enberg<penberg@xxxxxxxxxx>  wrote:
>>> On Wed, Jun 15, 2011 at 7:30 PM, Avi Kivity<avi@xxxxxxxxxx>  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:
>>>> 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.

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