Where can I find benchmarks on different networking architectures?

Question

Where can I find benchmarks on different networking architectures?

I am playing with sockets / threads / forks and I'd like to know what the best is. I was thinking there has got to be a place where someone has already spelled out all the pros and cons of different architectures for a socket service, listed benchmarks with code that runs.

Ultimately I'd like to run these various configurations with my own code and see which runs best in different circumstances.

Many people I talk to say that I should just use single threaded select. But I see an argument for threads when you're storing state information inside the thread to keep code simple. What is the trade off mark for writing my own state structure vs using a proven thread architecture.

I've also been told forking is bad... but when you need 12000 connections on a machine that cannot raise the open file per process limit, forking is an option! Forking is also a nice option for stability when you've got one process that needs restarting, it doesn't disturb the others.

Sorry, this is one of my longer questions... so many variables are left empty.

Thanks, Chenz

Answer 1

It's very difficult to answer this question as so much depends on what your service is actually doing. Does it have to query a database? read files from the filesystem? perform complicated calculations? go off and talk to some other service? Also, how long-lived are client connections? Might connections have some semantic interaction with other connections, or are they all treated as independent of each other? Might you want to think about load-balancing your service across multiple servers later? (If so, you might usefully think about that now so that any necessary help can be designed in from the start.)

As you hint, the serving machine might have limits which interact with the various techniques, steering you towards one answer or another. You have a per-process file descriptor limit, but remember that you may also have a fixed size process table! How many concurrent clients are you expecting, anyway?

If your service keeps crashing and you need to keep restarting it or you think you want a multi-process model so that connections are isolated from each other, you're probably doing it wrong. Stability is extremely important in this sort of context, and that means good practice and memory hygiene, both in general and in the face of network-based attacks.

Remember the history... fork() is cheap in the Unix world, but spawning new processes relatively expensive on Windows. OTOH, Windows threads are lightweight, whereas threading has always been a bit alien to Unix and only relatively recently become widespread.

Answer 2

edit: here's the link I was looking for, which is a whole paper answering your question. http://www.kegel.com/c10k.html

There are web servers designed along all three models (fork, thread, select). People like to benchmark web servers.

http://www.lighttpd.net/benchmark

Libevent has some benchmarks and links to stuff about how to choose a select() vs. threaded model, generally in favour of using the libevent model. http://monkey.org/~provos/libevent/