[cube2222]

I meant that you can have a multi-threaded runtime that will be executing your green threads in a multi-threaded fashion. Like in Go you have (by default) as many worker OS threads as CPUs, and the Go runtime will take care of scheduling your green threads on those worker OS threads (+ create threads as needed for blocking syscalls if I remember correctly, but that's getting way to deep into the details). And this will, in fact, "just work" from the user's perspective.

And yes, as both you said, and I said at the end of my previous comment, the main hurdle of green threads imo is FFI, but it's not what the article mentions, which is what surprised me.

[andygocke]

Ah, I see. You were saying that green threads can usually be scheduled on multiple os threads and take advantage of parallelism. Yup, I agree. Apologies for the confusion.