VirtIO Net Tuning

Hello All
  I have been playing with FreeBSD 14.3-RELEASE and 15.0-REELASE amd64 qemu
powered vms on a Linux cloud hosting setup. I have noticed that with VirtIO
net ( vtnet ) interfaces there is some sort of tuning required , or there
is some sort of limitation on the packets per second and overall throughput
the nics can push.  I am not able to get any one interface to push more
then 6Gb/s bursts and 5.5Gb/s sustained. Before I go off the deep end with
details has anyone run into this , is this a known issue ?

-- 
mark saad | nonesuch@longcount.org