[kqr]

> to a first approximation they all do basically the same thing; instead of giving you an array you have to iterate across they inform you about the sockets that are actually active

Well, that's half the story. The other half is that select/poll is stateless, meaning the application–kernel bridge is flooded with data about which events you are interested in, despite the fact that this set usually doesn't change much between calls.

kqueue and the like are stateful instead: you tell the kernel which events you are interested in and then it remembers that.

[abhishekjha]

Wait, so which is better? Stateful or stateless? How do you decide?

Very new to these APIs and their usages.

[kqr]

Stateless is simpler to implement and easier to scale across multiple nodes, but comes with additional overhead. When polling the kernel for sockets, the overhead was a bigger cost than implementation complexity and horizontal scaling. (Implementation complexity is still a problem – see the discussions regarding the quality of epoll; and horizontal scaling is just not something desktop kernels do.)

[mewse]

Good point, yes!