private void sumAtomicFromMultipleThreads() {
        Thread[] threads = new Thread[500];
        for (int i = 0; i < 500; ++i) {
            AtomicCounter c = new AtomicCounter();
            threads[i] = new Thread(c);
        }
        runAll(threads);
        System.out.println("Sum from all threads: " + atomicCounter.get());
    }
This just bangs on a shared to give some sort of lower bound for time
elapsed.
vespajlib/developernotes/ThreadLocalDirectoryBenchmark.java