Mark McLoughlin wrote:
On Thu, 2008-07-24 at 15:56 -0500, 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've just tried bridging to my physical LAN and DHCP seems to be working
fine.
Which reminds me, though - doing this makes host->guest throughput drop
to well below pre-GSO figures. GSO appears to be disabled while there's
a physical interface on the bridge. If I remove eth0, the figures jump
right back up again.
I also just noticed that the GSO patch breaks e1000 because it
unconditionally sets IFF_VNET_HDR. Will fix that up.
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
I tried iperf at one point and was getting really low figures; not sure
why.
Older iperf (~2.0.2) has locking vs yield bug and consumes lots of cpu.
In 2.0.4 it is fixed. Can that be the difference?
Apart from your iperf figures being lower than my netperf figures, it
also contradicts what I was seeing - namely guest->host beating
host->guest before the patches and host->guest beating guest->host after
the patches.
It could all just be down to the length of the tx timer. If you try
adjusting that does it help?
This is with KVM GUEST configured FWIW.
Yep, same here.
Cheers,
Mark.
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