And libev is a C wrapper around epoll and other system calls. There's not much code needed to use epoll directly, that's what John Fremlin's TPD2 web server (the previous "world's fastest Common Lisp web server") did:

https://github.com/vii/teepeedee2/blob/master/src/io/epoll.l...

What libev provides is a very portable wrapper around all the different non-blocking IO system calls in all the different Unixes. That's the hard part.