Slow networking on NOVA-vbox

Hi list!

I normally have 100 Mbps Internet, but on Nova-vbox it was initially about 10 Mbps. I revisited all network chain from iPXE Intel driver up to vbox/network.cpp. Ripped some (unneccessary for me) code from nic_drv, increased vbox prioprity to -1 (works great), use virtio instead of Intel PRO/1000, disable UART logging (on low level though). As a result, the best speed I've seen was about 25 Mbps while on my base Windows 7 I have exactly 100 Mbps in vbox for any guest.

So I have a question: is it Genode/NOVA architectural feature or I doing something wrong?

Thanks.