public Map<byte[], List<HStoreFile>> close(boolean abort) throws IOException {
    return close(abort, false);
  }
The following MAX_FLUSH_PER_CHANGES is large enough because each KeyValue has 20+ bytes
overhead. Therefore, even 1G empty KVs occupy at least 20GB memstore size for a single region
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java