private long getContainerMemDefaultMBytes() {
    Map<String, String> paramMap = _heuristicConfData.getParamMap();
    if (paramMap.containsKey(CONTAINER_MEM_DEFAULT_MB)) {
      String strValue = paramMap.get(CONTAINER_MEM_DEFAULT_MB);
      try {
        return Long.parseLong(strValue);
      } catch (NumberFormatException e) {
        logger.warn(CONTAINER_MEM_DEFAULT_MB + ": expected number [" + strValue + "]");
      }
    }
    return CONTAINER_MEMORY_DEFAULT_MBYTES;
  }
This heuristic deals with the efficiency of container size
app/com/linkedin/drelephant/mapreduce/heuristics/GenericMemoryHeuristic.java