I've used gevent in multiprocess situations, and it worked just fine. I did rig up my own gevent-based IPC, though. Just create a socketpair before forking, and attach some JSON-RPC (or protobuf/msgpack/etc) endpoints after.

You don't want multiprocessing to fork your process after gevent is loaded. If you can avoid that (like hold off on monkey patching) then it works great.