jason wang [off-list ref] wrote on 11/16/2011 11:40:45 AM:

Hi Jason,

Have any thought in mind to solve the issue of flow handling?

So far nothing concrete.

Maybe some performance numbers first is better, it would let us know
where we are. During the test of my patchset, I find big regression of
small packet transmission, and more retransmissions were noticed. This
maybe also the issue of flow affinity. One interesting things is to see
whether this happens in your patches :)

I haven't got any results for small packet, but will run this week
and send an update. I remember my earlier patches having regression
for small packets.

I've played with a basic flow director implementation based on my series
which want to make sure the packets of a flow was handled by the same
vhost thread/guest vcpu. This is done by:

- bind virtqueue to guest cpu
- record the hash to queue mapping when guest sending packets and use
this mapping to choose the virtqueue when forwarding packets to guest

Test shows some help during for receiving packets from external host and
packet sending to local host. But it would hurt the performance of
sending packets to remote host. This is not the perfect solution as it
can not handle guest moving processes among vcpus, I plan to try
accelerate RFS and sharing the mapping between host and guest.

Anyway this is just for receiving, the small packet sending need more
thoughts.

I don't recollect small packet performance for guest->local host.
Also, using multiple tuns devices on the bridge (instead of mq-tun)
balances the rx/tx of a flow to a single vq. Then you can avoid
mq-tun with it's queue selector function, etc. Have you tried it?

I will run my tests this week and get back.

thanks,

- KK