KVM and Libvirt: Bad CPU/Network performance of pgSense guest

lockheed

I have an Arch Linux host which runs virtualised router.

When using a LXC guest (linux) as router, everything is fine. I get 100MBits Up/Down and almost no CPU usage at all.

However, when I use libvirt gest (pfSense FreeBSD) as a router, whenever there is heavy network traffic going through the guest, the CPU usage goes unreasonably high (up to 100%) but the worst thing is that the network throughput is halved! I get 45-49Mbits max.

Host doesn’t support PCI pass through, so this is my config for the libvirtd VM:

    Nic1 (wan)
    Network source: Direct ‘eth0’
    Source mode: passthrough
    Device model: virtio

    Nic2 (lan)
    Bridge name: br0
    Device model: virtio

I tried e1000 instead but it changes absolutely nothing.

    Host CPU: AMD A4-5000 Kabini
    Guest CPU: default or Opteron_G3

Hardware polling in pfSense is disabled, and pfSense ifconfig shows this: http://storage5.static.itmages.com/i/16/1217/h_1481996196_8871112_a2f0d75655.png

This has been so since over a year now, since I started using pfSense as guest. If I do not solve this problem, I will have to dump libvirt/pfSense because such performance degradation is unacceptable.