protected final boolean isExceedSize(long sizeToCheck) {
    if (overallHRegionFiles) {
      long sumSize = 0;
      for (HStore store : region.getStores()) {
        sumSize += store.getSize();
      }
      if (sumSize > sizeToCheck) {
        LOG.debug("Should split because region size is big enough " + "sumSize={}, sizeToCheck={}",
          StringUtils.humanSize(sumSize), StringUtils.humanSize(sizeToCheck));
        return true;
      }
    } else {
      for (HStore store : region.getStores()) {
        long size = store.getSize();
        if (size > sizeToCheck) {
          LOG.debug("Should split because {} size={}, sizeToCheck={}", store.getColumnFamilyName(),
            StringUtils.humanSize(size), StringUtils.humanSize(sizeToCheck));
          return true;
        }
      }
    }
    return false;
  }
Returns true if region size exceed the sizeToCheck
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ConstantSizeRegionSplitPolicy.java