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 VM's 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? 

--
Alexey Tarasov

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