At which time and in which context should I call ThreadPool.SetMinThreads

Question

I have an ASP .NET MVC 2 - application, which calls functions of a C#-DLL.

The DLL itself is multithreaded. In the worst case it uses up to 200 threads, which do not run very long.

I use asynchronous delegates in order to generate the threads. In order to speed up the initialization of the delegates, I calculate the number of threads I need in advance and give it to the ThreadPool:

ThreadPool.SetMinThreads(my_num_threads, ...); 

I just wonder, if I need to do this early enough, such that the ThreadPool has enough time to create the threads? Do I have to consider, when I set the size of the ThreadPool or are the threads available immediately after I call SetMinThreads?

Furthermore, if I set the size outside the DLL in my ASP .NET MVC-application (before I call the DLL), will this setting be available/visible for the DLL?

Answer 1

They share the same application domain so that setting ThreadPool anywhere affects all. Note that this also impacts on the ASP.NET framework which will use ThreadPool itself for all its own async tasks etc.

With that in mind, if you knew roughly the minimum number of threads you wanted you could set that on application startup ready for use later on.

However, 200 threads seems somewhat excessive, to put it into context my Chrome with about 8 tabs open uses about 35 and my SQL Server ~50. What are you doing that demands so many?

Also realise that eventually you'll reach a limit where performance will degrade as there are so many threads that must be serviced. Microsoft says such on MSDN:

You can use the SetMinThreads method to increase the minimum number of threads. However, unnecessarily increasing these values can cause performance problems. If too many tasks start at the same time, all of them might appear to be slow. In most cases, the thread pool will perform better with its own algorithm for allocating threads. Reducing the minimum to less than the number of processors can also hurt performance.