Virtio network: poor performance with KVM hypervisor (latest Proxmox)

Hi all!

I am using the latest Proxmox 4.1 with all updates installed. I have several VMs with FreeBSD guests and 1 VM with Ubuntu 14 (all KVM). Host system file download speed: 60 MBps.

FreeBSD guest download speed: 2 MBps on virtio network with TSO enabled, 5-9 MBps with TSO disabled; 12 MBps on e1000 network. Ubuntu guest: 60 MBps with virtio.

I've tried the following:
  1. Different FreeBSD versions: 9.3, 10.2, 10.3-BETA3.
  2. Different TSO settings, enabling/disabling RXCSUM.
  3. Different TSO settings on host system.

The best results I got described above :(

Does anyone have any ideas how to get full network performance inside FreeBSD guests?