long lastAccessTime = 0;
      long lastWriteTime = 0;
      for (ReferenceEntry<K, V> e : segment.recencyQueue) {
        long accessTime = e.getAccessTime();
        assertTrue(accessTime >= lastAccessTime);
        lastAccessTime = accessTime;
        long writeTime = e.getWriteTime();
        assertTrue(writeTime >= lastWriteTime);
        lastWriteTime = writeTime;
      }