Re: Virtio network performance poorer than emulated e1000

Balachandar
2010-07-23T14:47:39Z

On Fri, Jul 23, 2010 at 9:37 AM, Sebastian Hetze <s.hetze@linux-ag.com> wrote:
> I did some benchmarking mainly with tbench and found virtio better
> with big packages/maximum throughput and e1000 better with small
> packages/latency. vhost-net improves virtio quite a lot and makes
> it superior to the emulated devices.
>

This is what that concerns me whether i am doing anything wrong.
vhost-net doesn't improve my virtio performance at all.. Thats what
makes me think that i am doing someting wrong. Couls you please tell
me the distribution, qemu-kvm version, guest and host kernel version,
no. of cores in cpu and your cpu info?

Actually my application is small packets and need low latency. I
cannot use dedicated network card for pci passthrough. I want to push
the virtio to work better for better latency for small packets. I dont
mind sacrificing throughput.
When i read that vhost-net reduces 4 to 5 times the latency of virtio,
i was excited but it didn't improve my latency at all.. I am
definitely missing something. Does vhost-net improves virtio latency
for small packets?

I tried disabling the tx timeout in the virtio-net in the qemu-kvm. It
did improve the latency a lot. But still it was far less than the
emulated e1000?

Is there any changes that can be made to virtio-net, vhost-net to
improve latency for small packets?

Thanks,
Bala