title: Performance problems using new fork join framework of jdk 7
body: <p>I'm using the new forkjoin framework of jdk 7.
  I got a task, which has to be performed multiple times with different parameters.</p>
  
  <p>This task extends <code>RecursiveTask</code>. there are more than 100 tasks to perform, which can performed concurrently. the tasks are independent, so there should be no need for any synchronisation. 
  Therefore I created at first the needed tasks and passed them to forkjoin thread pool.
  but the application becomes slower, than running it without any parallelism.</p>
  
  <p>My first thought was, that i create to much threads..  Thats why i tried to recycle the threads to reduce object creation overhead, but this has no effect on the performance. for recycling im using the reinitialize() method. Also with recycling the performance is slower than running it without any parallelism.</p>
  
  <p>The operations performed in the tasks are not trivial, the duration of running threads are from 5 to 150 ms.   The application runs on a dualcore machine and im using ubuntu and oracle jdk 7.</p>