public long totalSize() {
      return totalSize;
    }
Used to group blocks into priority buckets. There will be a BlockBucket for each priority
(single, multi, memory). Once bucketed, the eviction algorithm takes the appropriate number of
elements out of each according to configuration parameters and their relatives sizes.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/LruBlockCache.java