epoll VS select

Question

I have read a couple of networking books to get some idea of differences between epoll and select but they only covered this concepts slightly. I will be appreciated if you guys can provide me the key differences in details.

Thanks in advance

Answer 1

select is the standard Unix facility for doing asynchronous IO. Its programming interface is quirky, and its implementation in most Unixes is mediocre at best. It also imposes a limit on the maximum number of descriptors a process can watch, which is inconvenient in an application. Regarding efficiency, the performance of select usually degrades linearly with the number of descriptors.

epoll is a huge improvement over select in terms of programming interface and efficiency, but is only provided in Linux starting from version 2.6. Other Unixes have their specialised calls, too.