protected long heapSizeChange(Cell cell, boolean allocated) {
    long res = 0;
    if (allocated) {
      boolean onHeap = true;
      MemStoreLAB memStoreLAB = getMemStoreLAB();
      if (memStoreLAB != null) {
        onHeap = memStoreLAB.isOnHeap();
      }
      res += indexEntryOnHeapSize(onHeap);
      if (onHeap) {
        res += cell.heapSize();
      }
      res = ClassSize.align(res);
    }
    return res;
  }
@return The increase in heap size because of this cell addition. This includes this cell POJO's
        heap size itself and additional overhead because of addition on to CSLM.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/Segment.java