code: long refreshAndGetTotal() {
  		long total = 0;
  
  		for (ResultSubpartition part : partition.getAllPartitions()) {
  			total += part.unsynchronizedGetNumberOfQueuedBuffers();
  		}
  
  		return total;
  	}
docs: Iterates over all sub-partitions and collects the total number of queued buffers in a
  best-effort way.
  
  @return total number of queued buffers