Active Thread Number in Thread Pool

Question

When I write the below code, why do I get avaliable Thread number like 1022, 1020. I have to get 25 thread max as I am using thread pool.

I guess the ouput thread n

Answer 1

I have to get 25 thread max as I am using thread pool.

The maximum number of threads in the thread-pool per core has changed a lot over time. It's no longer 25 per core, which I suspect is what you were expecting.

For example, running this on my quad-core hyperthreaded laptop with .NET 4, I get a maximum of 32767 worker threads and 1000 IO completion port threads:

using System;
using System.Threading;

class Test
{
    static void Main()
    {
        int worker; 
        int ioCompletion;
        ThreadPool.GetMaxThreads(out worker, out ioCompletion);
        Console.WriteLine("{0} / {1}", worker, ioCompletion);
    }    
}

Under .NET 3.5 I get 2000 worker threads and still 1000 IO completion port threads.

That isn't the number of threads actually in the thread pool though - it's the maximum number that the thread pool allows itself to create over time.