Multithreaded server, bottleneck question

I am developing a multithread server which works nice so far - 1 separate thread for client accepting, threadpool for data rea开发者_Go百科ding and processing. Today I have added new thread for doing some stuff and sending messages to client every 500 ms (just 2-5 messages). I have noticed quite massive slowdown but Im not sure why - its separate thread and its not due to iteration and locking collections, because when I add //before SendMessage call, it was still as fast as before. The SendMessage basically iterates all connected clients and for each of them calls SendData method which writes data to their networkstream. What am I missing? I still think those are different threads and I hope its not due to stream.write.. Thank you in advance!

If you can try to post a code sample or a summary, your message sending implementation would make a good candidate.

First, purely general advice.

This is a good time to whip out a profiler. This kind of guessing is tempting, and often a good mental excercise, but most of the time programmers are wrong about what they think is making their software slow. A profiler will tell you, for example, if your program is spending 90% of its execution time inside of one method.

Second, a speculative guess.

It sounds like your message command runs off a timer. Make sure that you aren't having issues with reentrancy - for example if your sendmessage loop takes longer than 500ms to complete (and together with creating a new thread and multiple unpredictable latency network calls it could well do that), and you have the whole operation in a lock, then the timer will keep spawning off threadpool threads that are sitting in that lock waiting for the previous operation to complete - and there is a finite number of available threadpool threads. To check if this is a problem you don't even need a profiler, when latency gets bad pause the debugger and check up on your list of currently executing threads.

If this is the case consider doing something else - like have a single thread that runs in an infinite loop using a waithandle as a blocking mechanism and timer that sets the waithandle every 500ms.

But it will be much easier to help you if you post some code snippets, and run a profiler (Ants or DotTrace both work great).

Threads & threadpools for things like socket servers is the old way to do things. It's very unscalable (optimally you would like to not have more threads than cores), and full of locks.

Try converting your code to asynchronous code. You only need 1 thread, and you get callbacks whenever input arrives or when new data can be sent. The resulting code is much faster and doesn't have these bottleneck problems.

I know the advice of: no no, rewrite everything you should do it like this, is not really helpful, since it doesn't answer the exact question you asked. But if you do have the time, I still think it's a good advice. Or else, it's good advice for the next server you'll make ;^)