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Re: [libvirt-users] network-performance



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 cora nwra com
Boulder, CO 80301              http://www.cora.nwra.com


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