[libvirt-users] network-performance

Orion Poplawski orion at cora.nwra.com
Tue Feb 1 20:36:11 UTC 2011


On 02/01/2011 11:42 AM, Justin Clift wrote:
> On 02/02/2011, at 4:39 AM, Orion Poplawski wrote:
>> I'm just starting to take a look at guest networking performance and am a little disappointed.  I'm comparing two setups:
>>
>> Host: Windows Server 2008 R2 Hyper-V
>> Guest: CentOS 5.5 x86_64
>>
>> Host: CentOS 5.5 x86_64 kvm running libvirt
>> Guest: CentOS 5.5 x86_64
>>
>> The guests are essentially identical except that I'm running the Microsoft Linux Integration Components synthetic drivers on the windows hosted VM.  The libvirt setup uses bridged networking.  Running bonnie++ on a nfs mounted filesystem on each guest I'm seeing the libvirt hosted guest get between 16%-35% of the performance of the Hyper-V guest.  Is this expected?  Is there anything I can do to increase network performance of the kvm guest?
>
> Hi Orion,
>
> Just as an initial question, if the CentOS 5.5 guest using the VirtIO network drivers?
> It's been ages since I used CentOS 5.x, so I don't remember if they're the default or
> not.
>
> That's the initial "big performance boost" thing that's needed over the emulation type
> drivers.
>
> To check, take a look at the XML definition for the guest, and look at the networking
> interface.  There should be an element there called "model", and it will contain the
> type of network card being emulated.  If it's anything other than "virtio" then an
> emulated network driver interface is being used.  (not real fast)
>
> I'd give you a direct URL for the XML to reference, but ironically the libvirt.org server
> appears to be offline at the moment (doesn't happen very often thankfully!).  Heh.
>
> Hope that helps.
>
> Regards and best wishes,
>
> Justin Clift

Thanks a lot.  For some reason that particular machine was missing the crucial:

       <model type='virtio'/>

in the interface section.  Performance is much better now.

-- 
Orion Poplawski
Technical Manager                     303-415-9701 x222
NWRA/CoRA Division                    FAX: 303-415-9702
3380 Mitchell Lane                  orion at cora.nwra.com
Boulder, CO 80301              http://www.cora.nwra.com




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