A lot of the languages will probably perform similar on non-blocking I/O because they are all leveraging epoll (or select or kqueue) underneath it all. There is

A lot of the languages will probably perform similar on non-blocking I/O because they are all leveraging epoll (or select or kqueue) underneath it all. There is great variation however, on how the green threads are exposed. Node.js has callbacks, Python has yields, and Erlang has messages. Some of these approaches are easy to reason about and maintain than others. I always found Haskell's take on parallelism interesting, and maybe it is faster. In Haskell you create a unit of work called a 'spark'. You can have billions of these, they get mapped to lightweight Haskell threads (powered by epoll) and those get mapped onto OS threads.