Re: [PATCH 0/9][RFC] KVM virtio_net performance

Anthony Liguori
2008-07-24T18:29:57Z

Mark McLoughlin wrote:
> Hey,
> One all all-important thing I forgot to include was a comparison with
> lguest :-)
>

Hey Mark,

This patch set is really great! I guess the hard part now is deciding
what all we want to apply. Do you have a suggestion of which patches
you think are worth applying?

BTW, do you have native and guest loopback numbers to compare where we
stand with native?

> netperf, 10x20s runs (Gb/s) | guest->host | host->guest
> -----------------------------+----------------------------+---------------------------
> KVM | 4.230/ 4.619/ 4.780/ 0.155 | 8.140/ 8.578/ 8.770/ 0.162
> lguest | 5.700/ 5.926/ 6.150/ 0.132 | 8.680/ 9.073/ 9.320/ 0.205
>
> ping -f -c 100000 (ms) | guest->host | host->guest
> -----------------------------+----------------------------+---------------------------
> KVM | 0.199/ 0.326/ 7.698/ 0.744 | 0.199/ 0.245/ 0.402/ 0.022
> lguest | 0.022/ 0.055/ 0.467/ 0.019 | 0.019/ 0.046/89.249/ 0.448
>
>
> So, puppies gets you an extra 1.3Gb/s guest->host, .5Gb/s host->guest
> and much better latency.
>

I'm surprised lguest gets an extra 1.3gb guest->host. Any idea of where
we're loosing it?

> Actually, I guess the main reason for the latency difference is that
> when lguest gets notified on the tx ring, it immediately sends whatever
> is available and then starts a timer. KVM doesn't send anything until
> it's tx timer fires or the ring is full.
>

Yes, we should definitely do that. It will make ping appear to be a lot
faster than it really is :-)

Regards,

Anthony Liguori

> Cheers,
> Mark.
>
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