@Override
  public long heapSize() {
    // Will have to iterate over each element if RegionInfo implements HeapSize, for now it's just
    // a simple calculation.
    return sizeOfEntry * store.size();
  }
A {@link RegionSizeStore} implementation backed by a ConcurrentHashMap. We expected similar
amounts of reads and writes to the "store", so using a RWLock is not going to provide any
exceptional gains.
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/RegionSizeStoreImpl.java