public long wastedBytes() {
      return wastedBytes;
    }
If {@link #bucketCapacity} is not perfectly divisible by this {@link #itemSize()}, the
remainder will be unusable by in buckets of this size. A high value here may be optimized by
trying to choose bucket sizes which can better divide {@link #bucketCapacity}.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/bucket/BucketAllocator.java