Delegate.BeginInvoke Delay

Question

Sometimes when Delegate.BeginInvoke is invoked, it takes more than one second to execute the delegate method.

What could be the reasons for the delay? I get this issue 1 or 2 times a day in an application which runs continuosly.

Please help me.

Thanks!

Answer 1

The thread pool manager makes sure that only as many threads are allowed to execute as you have CPU cores. As soon as one completes, another one that's waiting in the queue is allowed to execute.

Twice a second, it re-evaluates what's going on with the running threads. If they don't complete, it assumes they are blocked and allows another waiting thread to run. On the typical two-core CPU, you'll get two threads running right away, the 3rd thread starts after one second, the 4th thread after 1.5 second, etcetera.

Well, there's your second. The Q&D fix is to use ThreadPool.SetMinThreads(), but that's the sledgehammer solution. The real issue is that your program is using thread pool threads for long-running tasks. Either because they execute a lot of code or because they block on some kind of I/O request. The latter being the more common case.

The way to solve it is to not use a thread pool thread for such a blocking thread but use the Thread class instead. Don't do this if the threads are actually burning CPU cycles, you'll slow everything down. Easy to tell, you'll see 100% cpu load in Taskmgr.exe