Re: how increase performance of network io in kvm

[Dor Laor <dor.laor@gmail.com>]

On Mon, 2008-03-10 at 12:13 -0700, Jorge Lucángeli Obes wrote:
> On Mon, Mar 10, 2008 at 11:58 AM, Dhirendra Pal Singh
> <dpal.singh@gmail.com> wrote:
> > Hi Guys,
> >
> > I am trying to evaluate, kvm at my work for virtual support in our product..
> >
> > I had setup up a windows guest, in my ubuntu host, on hardware with Intel VT
> > support.
> >
> > Now when I try to download a 1 GB file present, inside windows virtual
> > machine, using samba, from a another linux box, I get the following...
> >
> >
> > a) time when coping from windows in kvm
> >
> > linux:~/tmp # time cp /media/hdisk/1GB_text.txt .
> >
> > real    6m36.478s
> >
> > user    0m0.060s
> >
> > sys     0m8.293s
> >
> > linux:~/tmp #
> >
> >
> > b) time when coping from linux native..
> >
> >  linux:~/tmp/tmp # time cp /media/hdisk/1GB_text .
> >
> > real    0m49.501s
> >
> > user    0m0.040s
> >
> > sys     0m8.657s
> >
> > linux:~/tmp/tmp #
> >
> >
> > So its like 50second (linux native) Vs 6+minutes(windows guest in KVM),
> > which is huge.
> >
> > This is using user based networking, where I am just forwarding all the
> > netbios ports from host to guest.
> >
> >  Are there any links, pointers, faqs, ideas , suggestions I could try out to
> > increase the performance of this kvm virtual machine? Will using public
> > bridge (option 3), as described on page
> > http://kvm.qumranet.com/kvmwiki/Networking help?
> 
> Most probably. When I was trying VMGL
> (http://www.cs.toronto.edu/~andreslc/xen-gl/) in KVM I got a 20-fold
> increase in performance when I switched from usermode networking to
> the tap/bridge approach. Definitely try it. I assume you are forced to
> use a Windows guest, but if not you might also want to try virtio
> (http://kvm.qumranet.com/kvmwiki/Virtio).
> 


We published virtio network drivers for Linux but not yet for Windows.
Our virtio drivers for windows are almost done (for rev#1), we'll surely
release the binaries for them.

In the mean time you can use e1000 nic device & driver. It has the best
results among the emulated devices and even close to virtio performance.

Regards,
Dor


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