うーむうーむ。特にkern_fork.c.patch
http://people.freebsd.org/~davidxu/patch/?M=D
http://people.freebsd.org/~davidxu/patch/kern_fork.patch
http://people.freebsd.org/~davidxu/patch/calcru.patch
http://people.freebsd.org/~davidxu/patch/atfork.patch