VMOperationQueue::VMOperationQueue() {

  {- -------------------------------------------
  (1) フィールドの初期化
      ---------------------------------------- -}

      // The queue is a circular doubled-linked list, which always contains
      // one element (i.e., one element means empty).
      for(int i = 0; i < nof_priorities; i++) {
        _queue_length[i] = 0;
        _queue_counter = 0;
        _queue[i] = new VM_Dummy();
        _queue[i]->set_next(_queue[i]);
        _queue[i]->set_prev(_queue[i]);
      }
      _drain_list = NULL;
    }