I did hear back from a couple of really hardcore FreeBSD developers on the superpages fragmentation-during-fork() issue and their assessment was that it was a known issue caused by contention for the pages between the parent and child process between fork() and exec(). They (surprise, surprise) recommended the use of vfork() to workaround the issue. So, as uncomfortable as that makes me, I guess it's the right way to go, at least on FreeBSD. Thanks!
