code: @Override
  	public void releaseMemory(int toRelease) throws IOException {
  		checkArgument(toRelease > 0);
  
  		for (ResultSubpartition subpartition : subpartitions) {
  			toRelease -= subpartition.releaseMemory();
  
  			// Only release as much memory as needed
  			if (toRelease <= 0) {
  				break;
  			}
  		}
  	}
docs: Releases buffers held by this result partition.
  
  <p>This is a callback from the buffer pool, which is registered for result partitions, which
  are back pressure-free.