@Override
  public int getLocalSize() {
    return getRegionMap().size() - tombstoneCount.get();
  }
(description copied from entryCount() Returns the number of entries in this region. Note that
because of the concurrency properties of the {@link RegionMap}, the number of entries is only
an approximate. That is, other threads may change the number of entries in this region while
this method is being invoked.

@see LocalRegion#entryCount()
geode-core/src/main/java/org/apache/geode/internal/cache/LocalRegion.java