In the mean
That's what I've discovered as well, TrueNas 12 windows vm performance was much better, it was usable, I wonder when stable version is out, will we be able to upgrade without redoing preexisting jails and VMs?
I tried that too, and it is better, although I have not tried using virtio for block devices. So maybe after 12 update 1 o update 2 I will switch because I'm really looking for that. It would be nice to have the nvme emulation that freebsd 12 supposedly gets, tough.
On the other hand, I noticed that power management also messes up with performance even in linux/freebsd virtual machines.
It's always been annoying that bhyve actually prevents the processor to ever scale frequency down, so I always put a limitation in cpu freq via powerd_flags in rc.conf tunable if I don't actually need the full power of the cpu. It costs a lot more to run it at 3300mhz vs 2200mhz. Just by chance, I happened to stop powerd and set the frequency via sysctl because I needed more juice for a test, and I noticed it also works marginally better in 11.3 if you just tell powerd to use a fixed frequency.