A DESCRIPTION OF THE REQUEST :
I'm seeing a slow down of Object.hashCode with it taking over twice as long to compute the default hash code running 4 threads vs 1 thread for the same number of objects.

JUSTIFICATION :
Multi threading is becoming more common so this kind of thing is good to fix.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I'd hope it would take a similar amount of time doing this in parallel.
ACTUAL -
Run the attached test. You can change the number of threads. Each thread has the same amount of work to do so you'd hope that running 4 threads on a quad core machine might take about the same time as running a single thread. I'm seeing ~2.3 seconds for 4x but .9 s for 1x.

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import java.util.Arrays;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadFactory;


public class ObjectHashCodePerformance {

  private static final int THREAD_COUNT = 4;
  private static final int ITERATIONS = 20000000;

  public static void main(final String[] args) throws Exception {
    long start = System.currentTimeMillis();
    new ObjectHashCodePerformance().run();
    System.err.println(System.currentTimeMillis() - start);
  }

  private final ExecutorService _sevice = Executors.newFixedThreadPool(THREAD_COUNT, new ThreadFactory() {
    private final ThreadFactory _delegate = Executors.defaultThreadFactory();
    @Override
    public Thread newThread(final Runnable r) {
      Thread thread = _delegate.newThread(r);
      thread.setDaemon(true);
      return thread;
    }
  });

  private void run() throws Exception {
    Callable<Void> work = new java.util.concurrent.Callable<Void>() {
      @Override
      public Void call() throws Exception {
        for (int i = 0; i < ITERATIONS; i++) {
          Object object = new Object();
          object.hashCode();
        }
        return null;
      }
    };
    @SuppressWarnings("unchecked")
    Callable<Void>[] allWork = new Callable[THREAD_COUNT];
    Arrays.fill(allWork, work);
    List<Future<Void>> futures = _sevice.invokeAll(Arrays.asList(allWork));
    for (Future<Void> future : futures) {
      future.get();
    }
  }

}

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