Maximum number of threads in a JVM?

Question

What are the maximum number of threads which can be maintained by the Java virtual machine?

I did not explain this in my original question, but I am trying to benchm

Answer 1

Maximum thread limit mainly depends on hardware, OS and Java stack size.

The following factor plays a very important role to identify max thread limit:-

1. Process virtual address limit (2^32 for 32-bit architecture and 2^64 for 64-bit architecture)
2. Java stack size (can be determine by command java -XX:+PrintFlagsFinal -version | grep -iE 'ThreadStackSize'
3. Max PID limit (can be determine by command "cat /proc/sys/kernel/pid_max")
4. Max process limit ulimit -u

So max thread limit will be MINIMUM of ((process virtual address space/java stack size), Max PID limit, Max process limit)

e.g. if Max process limit is 2048 and it is minimum of all above mention three-factor then java process will not be able to create a thread more than that.

To verify it one can create simple java application in which he/she can create a thread in a loop and see how much it can go.

Example:

public class ThreadCountTest {
  private static final Object lock = new Object();
  private static int counter = 0;
    
  public static void main(String[] _args) {
    while (true) {
      new Thread(new Runnable() {
        public void run() {
          synchronized(lock) {
            counter++;
            System.err.println("New thread #" + counter);
          }
          while (true) {
            try {
              Thread.sleep(3000);
            } catch (Exception e) {
              e.printStackTrace();
            }
          }
        }
      }).start();
    }
  }
}