Can we create 300,000 threads in a C# application and run it on a PC?

Question

I am trying to imitate a scenario where 300,000 consumers are accessing a server. So I am trying to create the pseudo clients, by repeatedly querying the server from the concurrent threads.

But the first hurdle to be cleared is, whether it is possible to run 300,000 threads on a PC? Here is a code which I am using to see intially how many max threads I can get, and later then replace the test function with the actual function:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace CheckThread
{
    class Program
    {
        static int count;

        public static void TestThread(int i)
        {
            while (true)
            {
                Console.Write("\rThread Executing : {0}", i);
                Thread.Sleep(500);
            }
        }

        static void Main(string[] args)
        {
            count = 0;
            int limit = 0;
            if (args.Length != 1)
            {
                Console.WriteLine("Usage CheckThread <number of threads>");
                return;
            }
            else
            {
                limit = Convert.ToInt32(args[0]);
            }
            Console.WriteLine();
            while (count < limit)
            {
                ThreadStart newThread = new ThreadStart(delegate { TestThread(count); });
                Thread mythread = new Thread(newThread);
                mythread.Start();
                Console.WriteLine("Thread # {0}", count++);
            }

            while (true)
            {
                Thread.Sleep(30*1000);
            }
        } // end of main
    } // end of CheckThread class
} // end of namespace

Now what I am trying might be unrealistic, but still, if there is a way out to do it and you know, then please help me.

Answer 1

Each thread will create its own stack and local storage, you are looking at roughly 512k of stack space per thread on a 32bit OS, I think the stack space doubles on a 64 bit OS. A quick back of the spreadsheet calc gives us 146.484375 gigs of stack space for your 300k clients.

So, no, don't create 300k threads, but rather use the threadpool to simulate 300k requests, although tbh I think you would be better off with several test clients spamming your server through a network interface.

There are a lot of web load-testing tools available. Good starting point : http://www.webperformance.com/library/reports/TestingAspDotNet/

Answer 2

You can alter the maximum nunmber of threads by calling the ThreadPool.SetMaxThreads method. 300,000 threads will probably make your PC explode*

*This is probably an exaggeration

Answer 3

Language-agnostic answer:

The better way to probably go about this is using the Reactor pattern, with a maximum of 1 or 2 concurrent threads per core.

Answer 4

As .net commits the entire stack (1MB) for each clr thread; as Ben says, your PC may actually explode. Or possibly OoM.