private void checkNegativeMemStoreDataSize(long memStoreDataSize, long delta) {
    // This is extremely bad if we make memStoreSizing negative. Log as much info on the offending
    // caller as possible. (memStoreSizing might be a negative value already -- freeing memory)
    if (memStoreDataSize < 0) {
      LOG.error("Asked to modify this region's (" + this.toString()
        + ") memStoreSizing to a negative value which is incorrect. Current memStoreSizing="
        + (memStoreDataSize - delta) + ", delta=" + delta, new Exception());
    }
  }
Increase the size of mem store in this region and the size of global mem store
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java