@Override
        public Cacheable deserialize(ByteBuff b, ByteBuffAllocator alloc) throws IOException {
          int len = b.getInt();
          Thread.yield();
          byte buf[] = new byte[len];
          b.get(buf);
          return new ByteArrayCacheable(buf);
        }
Just checks if heapsize grows when something is cached, and gets smaller when the same object
is evicted
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/CacheTestUtils.java