vtnet is still slow

Hi,

I wondered if any work was happening to address the long-standing issue
of slow vtnet? (in my case, this leads to slow freebsd guest performance
in bhyve compared with every linux guest tested and OpenBSD).

I thought maybe the recent bridge work may have ameliorated the problem 
some, but testing, after configuring a (recent) stable/15 server to use the 
ip-configured-on-bridge-method, showed no improvement using
a (recent) stable/14 guest

[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-60.03  sec  3.17 GBytes   454 Mbits/sec    0     sender
[  5]   0.00-60.03  sec  3.17 GBytes   454 Mbits/sec          receiver

for comparison, an ubuntu 25.04 guest:

[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-60.00  sec  6.42 GBytes   919 Mbits/sec  5427    sender
[  5]   0.00-60.00  sec  6.42 GBytes   919 Mbits/sec          receiver

the baremetal host

[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-60.01  sec  6.58 GBytes   941 Mbits/sec    0     sender
[  5]   0.00-60.01  sec  6.58 GBytes   941 Mbits/sec          receiver

Tests done a year and a half ago on similar hardware showing
the same patterns http://void.f-m.fm.user.fm/bhyve-virtio-testing.html
--