code: public static Heap createFastHeap(File heapDump, long bufferSize) throws FileNotFoundException, IOException {
          return new FastHprofHeap(createBuffer(heapDump, bufferSize), 0);
      }
docs: Fast {@link Heap} implementation is optimized for batch processing of dump.
  Unlike normal {@link Heap} it doesn't create/use any temporary files.
  
  @param bufferSize if file can be mapped to memory no buffer would be used, overwise limits memory used for buffering