Re: virtio-net working on PowerPC KVM

Avi Kivity
2008-03-30T10:31:04Z

Hollis Blanchard wrote:
> I'm pleased to report that we now have working network support in the
> guest, via the virtio-net driver. In fact, we can use NFS for the
> guest's root filesystem. :) Boot log attached.
>
>

Congrats!

> The bad news is that it's very slow, but the good news is that it's nice
> to be improving performance rather than debugging mysterious
> crashes... ;)
>
> With this milestone reached, in the near future I intend to start
> sending patches to Avi and linuxppc-dev for review, hopefully for
> inclusion in 2.6.26. However, I do want to see if we can improve the
> performance a little bit first...
>

Low virtio net performance may be due to the virtio net host timer.
What's your guest/host ping latency?

Even if you have a good hrtimer implementation, I think you'll see
0.25ms latency, and that may be enough to slow down nfs. Unfortunately
virtio is tuned for throughput at this time (it should be easy to
disable the timer when we detect the queue is usually empty).

--
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