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

Bill Davidsen
2008-07-26T19:08:23Z

Anthony Liguori wrote:
> Hi Mark,
>
> Mark McLoughlin wrote:
>> Hey,
>> Here's a bunch of patches attempting to improve the performance
>> of virtio_net. This is more an RFC rather than a patch submission
>> since, as can be seen below, not all patches actually improve the
>> perfomance measurably.
>>
>
> I'm still seeing the same problem I saw with my patch series. Namely,
> dhclient fails to get a DHCP address. Rusty noticed that RX has a lot
> more packets received then it should so we're suspicious that we're
> getting packet corruption.

I have been discussing this (on this list) in another thread. Putting
tcpdump on the eth0 device in the VM, the br0 device in the host, and
the eth0 (physical NIC) in the host, you can see that when the VM
generates a DHCP request it shows up on the br0 in the host, but never
gets sent on the wire by eth0.

That's the point of failure, at least using RHEL5/FC6/kvm-66 as the
environment.
>
> Configuring the tap device with a static address, here's what I get with
> iperf:
>
> w/o patches:
>
> guest->host: 625 Mbits/sec
> host->guest: 825 Mbits/sec
>
> w/patches
>
> guest->host: 2.02 Gbits/sec
> host->guest: 1.89 Gbits/sec
>
> guest lo: 4.35 Gbits/sec
> host lo: 4.36 Gbits/sec
>
> This is with KVM GUEST configured FWIW.
>
> Regards,
>
> Anthony Liguori
>

--
Bill Davidsen <davidsen@tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot