public void initialize(ByteBuffer byteBuffer, int offset, int length) {
    this.byteBuffer = byteBuffer.slice();
    this.byteBuffer.position(offset);
    this.byteBuffer.limit(offset + length);
    this.allocSize = length;
  }
Allocator uses this to remember the allocation size. Somewhat redundant with header.
llap-server/src/java/org/apache/hadoop/hive/llap/cache/LlapAllocatorBuffer.java