[strmpnk]

It's definitely true, though likewise, it's expensive to use locks in such places too. The main idea with Pony's runtime is that contending for an actors attention will certainly incur costs but independent pairs of actors should not, even during GC.

I also glossed over the I/O system and back pressure support which make the above discussion a bit more nuanced but my goal was to lay down some form of intuition around thinking in terms of progress in a system as a guarantee of the concurrency model.

Empirically speaking, there are real limits to what hardware will hide and plenty of room for leveraging knowledge of the system as a whole (esp. the memory model) rather than sticking to one set of abstractions. Pony is no exception here, though the co-design of various features might make that less necessary than it might be in other systems with similar properties as it matures.