Java OutOfMemoryError :Unable to create new native thread, JVM Exception/Error

This is continuing article of out of memory error explanation. In this post I will provide how to reproduce Java OutOfMemoryError :Unable to create new native thread . We will see how to recreate and what are the impact in monitoring tools.

I have used JVM 1.6 x64 & JVM 1.8 x64 on windows 7 x64/8gb ram/ 2.5Ghz Core i5 laptop.

Tools : IDE : Eclipse
Profiling/Monitoring tool :1. Visual VM
2. Jconsole (optional)
3. Yourkit (optional)

I am using some JVM flags to get detail GC information and monitoring via JMX. Please see this post in step 1 for detail.

Now, for the nature of the error, it is easily untestable , due to PC’s limitations, JVM is unable to create new thread. Again, to know about the error, you can visit this original post.

Scenario :
I will write a function which will actually create many threads, start them, make them a demon thread(so that they are kept running) and store all thread in a collection. So that , the number of thread grows and we can get the error.

Code :

public class ThreadOOM {
    public static void createOOMbyThread(){
        List allThreads = new ArrayList();
        try{
        while(true)
        {
            long startTime = System.currentTimeMillis();//to know timing is optional
            Thread aThread = new Thread(new Runnable(){// Anonymous runnable class
                  @Override
                  public void run() {
                      //System.out.println("Thread is running");
                    try {
                      while (!Thread.interrupted())//this will sleep the thread untill it is stopped.
                      {
                        Thread.sleep(1);
                      }} catch (InterruptedException ignored) {}}});
                aThread.setDaemon(true);
                aThread.setPriority(Thread.MIN_PRIORITY);
                allThreads.add(aThread);
                aThread.start();
            long endTime = System.currentTimeMillis();//to know timing is optional
            Thread.sleep(1);//if you need more wait, you can avoid to have quick impact
            System.err.println("Total Thread = "+allThreads.size()+" Required time(ms) = "+(endTime-startTime));
        }
        }catch(Throwable e){
            System.err.println("\nError at "+ allThreads.size()+" threads");
            e.printStackTrace();
        }
}}

And from main method , just call

ThreadOOM.createOOMbyThread();

Source in Github.

Error analysis in console :

Java 6 : Error happened in 3007 thread.

BTW, this number is not same always, it is based on CPU/Memory load. When I attached yourkit agent , it was less in numbers.

Java 8 : Amazingly, Java 8 went up to 200906 thread. For less delay, I commented thread delay (2nd one) so that it moves faster. My PC become very slow resource usages were very very high. It seems Java 8 have separate mechanism to provide very high performance.

Java 6 Monitoring in Visual VM :

I attached visual VM next time, and got error 3015 threads. So, the console error.

As, JVM run user application by its own demon threads, so, in visual VM the count is little extra to 3030 (our created demon threads + predefined demon threads)

And, if we look at GC activity, we can see how much CPU it was taking

You may noticed, 727% , actually JVM consider single thread as 100% CPU usages. And if you have multiple core or thread, it will multiply. In case of tweak/boost/overclock CPU it will increase the %. As my CPU was Core i5 2.5Ghz to boostable upto 3.1Ghz and when JVM starts it used to be running below 2Ghz. So, overall, it multiply single CPU thread performance and number of thread.

And heap usages

PermGen usages

Java 6.0 Monitoring in Yourkit:

When I attached your kit the thread OOM happened in 2228 threads and heap was this.

As, yourkit has some initial delay to attach with application, if we see from your kit, we may see less number of thread. In my case it was 2185.

and this was Heap usages

Java 8 Monitoring :
Visual VM : When I used visual VM, OOM occurred after 189772 threads but, it also cased

1. stack over flow error

2. Visual VM crashed

So, in that I should say, it was possible to create OOM with profiler but not possible properly to diagnosis. Similar story happened for Your kit also.

These are exceptions from log (in case you are interested)