http://news22.2ch.net/test/read.cgi/liveplus/1177641490/744
やはり，これは panic するんじゃなくて本来エラーリターンするようにすべきもの，ってことですね．

panic: vm_thread_new: kstack allocation failed
http://lists.freebsd.org/pipermail/freebsd-threads/2006-September/003700.html
> I've seen this when running stress2 with a large number of
> incarnations. Why don't we return an error to the user?


programmer ENOTIME

patch welcome!

http://lists.freebsd.org/pipermail/freebsd-threads/2006-September/003701.html
On closer inspection this means that we've run out of KVA. In
principle it should be handled more gracefully, but the 1GB KVA
limitation is really a 32-bit artifact. It might be worth wading
through the kernel memory allocations to see if a subsystem has gone
beserk.