I just saw on Digg this interesting a link to an interesting new open source operating system, Helen OS. Among other things, HelenOS has support for SMP, Kernel threads, userspace threads, userspace pseudo-threads ("Userspace pseudo threads are very lightweight threads running in the context of one userspace thread") and IPC ("the ability of userspace threads to communicate with other threads (possibly from different tasks) via sending and receiving, synchronously or asynchronously, short messages"). The full list is here.
Some of these features strike me as very similar to those that provided by Erlang and its virtual machine. I wonder if HelenOS developers took some cues from Erlang's success at scaling to large numbers of concurrent processes by keeping them very lightweight. This raises the interesting question of whether such features, when provided by the OS, make it possible to write C/C++ programs with the same scalability characteristics as Erlang programs at large numbers of concurrent processes. I should stress that the operative word here is "possible" -- not "easy"!
Let's sit back and wait for the benchmarks.