public int getItemAllocationSize() {
      return itemAllocationSize;
    }
This class is used to allocate a block with specified size and free the block when evicting. It
manages an array of buckets, each bucket is associated with a size and caches elements up to this
size. For a completely empty bucket, this size could be re-specified dynamically.
<p/>
This class is not thread safe.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/bucket/BucketAllocator.java