docs: @Benchmark
    @BenchmarkMode(Mode.SampleTime)
    @OutputTimeUnit(TimeUnit.NANOSECONDS)
    public void manyRunnables() throws Exception {
      incrRunnable.val = 0;
      for (int i = 0; i < 500; i++) {
        executor.execute(incrRunnable);
      }
      executor.execute(phaserRunnable);
      phaser.arriveAndAwaitAdvance();
      if (incrRunnable.val != 500) {
        throw new AssertionError();
      }
    }