> That's incorrect, most scheduling systems, including OS threads are preemptive. Erlang's scheduler itself is actually cooperative - though it can still preemp

> That's incorrect, most scheduling systems, including OS threads are preemptive. Erlang's scheduler itself is actually cooperative - though it can still preempt the "processes" it schedules. OS processes are preemptive, however process threads are not. I'm not sure what you are trying to say about Erlang's scheduler itself being cooperative. It is a preemptive scheduler. > Erlang's message passing system is probably more important to the success of its concurrency model than the specifics of the scheduler. I disagree, preemptive concurrency is a fundamental piece of BEAM's success. Preemption gives Erlang its fault tolerance and low latency guarantees. If by message passing you mean immutability, then perhaps they are of equal importance.