The issue with select(2)/poll(2) (and for that matter WaitForMultipleObjects()) is that you are passing huge datastructure across userspace/kernel boundary with

The issue with select(2)/poll(2) (and for that matter WaitForMultipleObjects()) is that you are passing huge datastructure across userspace/kernel boundary with each call. There are various alternative platform specific implementations of what in the end is still polling that place the set of interesting FDs on the kernel side and thus make the whole thing significantly faster. That is what libev/libevent/libuv abstracts away in portable manner. The programming style is essentially same for a program that uses select(2) directly. (If you do not count various anti-patterns that are common in GUI applications which do networking)