Browse Prior Art Database

Implementation of High Performance Subtype Object Migration

IP.com Disclosure Number: IPCOM000116861D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 141K

Publishing Venue

IBM

Related People

Chen, C: AUTHOR [+3]

Abstract

A high performance capability to "migrate" from one subtype object to another is disclosed. This subtype migration scheme combines the creation of a new subtype instance and the deletion of an old subtype instance to significantly improve performance.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 37% of the total text.

Implementation of High Performance Subtype Object Migration

      A high performance capability to "migrate" from one subtype
object to another is disclosed.  This subtype migration scheme
combines the creation of a new subtype instance and the deletion of
an old subtype instance to significantly improve performance.

      In an object oriented real time system with a great deal of
object creation and deletion, the performance impact due to new
instance memory allocation, initialization, and deallocation can
become very significant.  In an object oriented system, most objects
exist within specific "supertype/subtype" hierarchies that provide
for attribute inheritance.  Subtype objects inherit attributes from
supertype objects.

      Subtype objects often change to a different subtype object
within the same "supertype/subtype" hierarchy during their life
cycles.  This process is called "subtype migration" and normally
would contain the following steps:
  o  Subtype A creates an instance of the new subtype, called subtype
      B.  This involves a call to memory management services to
      allocate system memory for subtype B.  The new instance is
added
      to system controlled instance lists for subtype B.
  o  All of the attributes for the new instance must now be
      initialized.  This includes those that are common with the same
      supertype object(s) and currently contained in subtype A.
  o  After all attributes have been initialized, subtype A must be
      deleted.  It must be removed from the system controlled
instance
      lists for subtype A.  Next, another call is made to memory
      management services to deallocate or release subtype A's memory
      area.
  o  All references to subtype A maintained by other objects must now
      be updated to reflect the identifier of subtype B.

The specific drawbacks of this approach are:
  o  Memory management services are called twice (allocation and
      deallocation).
  o  Both instances are simultaneously present (and in system
      controlled instance lists) for a short period of time.
  o  Common (i.e., inherited) attributes must be physically copied
      from subtype A's memory area to subtype B's memory area.
  o  Object references must be updated to reflect the new subtype
      identifier (significant complexity which may involve the
addition
      of other events).

      A high performance capability to "migrate" from one subtype
object to another has been developed.  This new subtype migration
scheme combines the creation of a new subtype instance and the
deletion of an old subtype instance to significantly improve
performance.  The performance improvement occurs because the same
physical memory locations are used and memory management functions
are not called.  An additional performance improvement may be
realized if the object being migrated is c...