virtualbox tips for performance specific to FreeBSD-10 hosts

[John]

Hello list,

As subject, can anyone recommend any tips for getting optimum
performance from various guests on a freebsd-10-R host? I've looked at
the page about changing polling interval but that only applies to
freebsd guests. I'm looking advice specifically for linux guests on this
host. Guests are ubuntu and opensuse.

Machine is a Xeon E5-2650L @ 1.80GHz with 32 cores, 192GB RAM and 10TB
available storage on zfs.

No issues sofar freebsd on freebsd. Just looking for advice linux guest
on freebsd with virtualbox. Or perhaps there's something better than
virtualbox? Basically all guests need to be isolated from one another.
It makes backing up and restoring systems pain-free.

thanks,
-- 
John