private void updateRegionCachedSize(Path filePath, long cachedSize) {
    if (filePath != null) {
      String regionName = filePath.getParent().getParent().getName();
      regionCachedSize.merge(regionName, cachedSize,
        (previousSize, newBlockSize) -> previousSize + newBlockSize);
    }
  }
This method is invoked after the bucketEntry is removed from {@link BucketCache#backingMap}
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/bucket/BucketCache.java