long startTime = System.nanoTime();
    long ns = millis * 1000 * 1000;
    for (; ; ) {
      if (millis > 0L) Thread.sleep(millis);
      else // too short to sleep
      Thread.yield();
      long d = ns - (System.nanoTime() - startTime);
      if (d > 0L) millis = d / (1000 * 1000);
      else break;
    }
  }