-ENOMEM on pthread_create

[Ferguson, Neale]

I have a program that attempts to spawn several hundred threads. When it
gets to 445 it complains about not enough storage. Okay. I up the guest from
256M to 384. No luck, same problem. I set kernel.thread-max up to 16384.
Still no good. I up the ulimit on the stacksize to unlimited. No joy either.
Does anyone have any suggestions as to what knob to twiddle?