Network performance using virtio nic

Hi all,

What kind of network speeds can I expect using the virtio nic?  I have rhel 6.3 guests running under rhev 3.0 on HP BL460c Gen8 blades.  The blades have 10G nics.  In a rhel 6.3 bare-metal installation, I can get over 2.5gbps throughput between blades using udp (the speed is capped at 3gbps by the ethernet module (Flex-10) in the blade chassis, btw).  On the same hardware, my rhel 6.3 guests can only achieve around 1.5gbps transfer rate between VMs before suffering packets drops.  This is my max rate whether my VMs are on the same or different blades.

My guests are not constrained by CPU (~15% utilization at these rates), but the network utilization meters in rhevm are pegged at 100%.  Is there some perfomance tuning I can do on the virtio driver or guest o/s nic interface?

As a point of comparison, I can get rates in excess of 2gbps on the same hardware under vmware esxi 5.1 using their paravirtulaized nic.  

Cheers,

Steve.