select vs poll vs epoll

Question

I am designing a new server which needs to support thousands of UDP connections (somewhere around 100,000 sessions). Any input or suggestions on which one to use?

Solution 1

The answer is epoll if you're using Linux, kqueue if you're using FreeBSD or Mac OS X, and i/o completion ports if you're on Windows.

Some additional things you'll (almost certainly) want to research are:

• Load balancing techniques
• Multi-threaded networking
• Database architecture
• Perfect hash tables

Additionally, it is important to note that UDP does not have "connections" as opposed to TCP. It would also be in your best interest to start small and scale larger since debugging network-based solutions can be challenging.

Solution 2

The author of CURL wrote an amazing article on poll vs select vs event libraries.

Solution 3

Linux: epoll FreeBSD: kqueue Windows: ??

There are wrapper libraries, such as libevent and libev, which can abstract this for you.

Comments

[Krystian Bigaj]

Windows: IO Completion Port

[Admin]

Thanks for the response. I understand there is no such thing called UDP connections as it is a connectionless oriented communicated. The application I had in mind is session based, so instead of session I mentioned it as connection. My bad. Also I have tried more than 200,000 sessions based on select with multithreaded application. Just wanted to optimize. Also iam not new to building scalable architecture solution. Load balancing might not be good fit for the kind of server iam looking at. It’s definitely a multithread networking. Will most probably use some kind of producer/consumer pattern.

[Soonts]

And by the way. IOCP: Windows NT 3.5, 1994; kqueue: BSD 4.1, 2000; epoll: linux kernel 2.5.44, 2002.

[unixman83]

libev is poorly written IMO, it crashes when I free memory for active events after I've stopped them! The design is not good. Also, It's all in one (3000 line) .c file that contains most of the code.

[Navin]

@unixman83 A single 3000 line .c file sounds amazing!

[enigmaticPhysicist]

That guide didn't help at all. It basically assumed everybody knew the main differences between the three.

[MikeMB]

Please provide at least a summary and not just a bare link

[Guy Avraham]

@enigmaticPhysicist - I agree with you. I have found this article more detailed, hope it helps: ulduzsoft.com/2014/01/…