Can you have too many Delegate.BeginInvoke calls at once?

I am cleaning up some old code converting it to work asynchronously.

psDelegate.GetStops decStops = psLoadRetrieve.GetLoadStopsByLoadID;
var arStops =开发者_开发百科 decStops.BeginInvoke(loadID, null, null);
WaitHandle.WaitAll(new WaitHandle[] { arStops.AsyncWaitHandle });
var stops = decStops.EndInvoke(arStops);

Above is a single example of what I am doing for asynchronous work. My plan is to have close to 20 different delegates running. All will call BeginInvoke and wait until they are all complete before calling EndInvoke.

My question is will having so many delegates running cause problems? I understand that BeginInvoke uses the ThreadPool to do work and that has a limit of 25 threads. 20 is under that limit but it is very likely that other parts of the system could be using any number of threads from the ThreadPool as well.

Thanks!

No, the ThreadPool manager was designed to deal with this situation. It won't let all thread pool threads run at the same time. It starts off allowing as many threads to run as you have CPU cores. As soon as one completes, it allows another one to run.

Every half second, it steps in if the active threads are not completing. It assumes they are stuck and allows another one to run. On a 2 core CPU, you'd now have 3 threads running.

Getting to the maximum, 500 threads on a 2 core CPU, would take quite a while. You would have to have threads that don't complete for over 4 minutes. If your threads behave that way then you don't want to use threadpool threads.

The current default MaxThreads is 250 per processor, so effectively there should be no limit unless your application is just spewing out calls to BeginInvoke. See http://msdn.microsoft.com/en-us/library/system.threading.threadpool.aspx. Also, the thread pool will try to reuse existing threads before creating new ones in order to reduce the overhead of creating new threads. If you invokes are all fast you will probably not see the thread pool create a lot of threads.

For long running tasks or blocking tasks it is usually better to avoid the thread pool and managed the threads yourself.

However, trying to schedule that many threads will probably not yield the best results on most current machines.