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


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