> you are talking about OS level selectors (epoll), in which case you are going to run up against OS limitations.

Yes, about them, but I’m not sure what OS limitations do you mean?

For Windows, it works fine from the very first NT 3.51 version of IOCP.

For Linux it indeed didn’t work in the very first version of epoll, but they fixed that adding EPOLLONESHOT flag, and recently EPOLLEXCLUSIVE flag for accept(), allowing to implement proper scaling of IO readiness notifications across multiple CPU cores.