Method for the relocation of linked control blocks

• US 4,833,604 A
• Filed: 01/13/1986
• Issued: 05/23/1989
• Est. Priority Date: 01/13/1986
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Nomm, Nicholas V., Yothers, Jay A., Cheng, Josephine M.
• Primary Examiner(s): Heckler, Thomas M.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/818,432
• Time in Patent Office: 1,226 Days
• Field of Search: 364/200 MS File, 364/300, 364/900 MS File
• US Class Current: 1/1
• CPC Class Codes: G06F 9/44521 Dynamic linking or loading; Link editing at or after load time, e.g. Java class loading

Abstract

A two-pass method for relocating a set of linked control blocks stored away on a persistent medium after a first pass and then rewritten into internal memory of a computing facility during second and subsequent passes each time an application to which the control blocks are bound is executed. The first pass involves path following and coloring pointers affected by the relocation, mapping discontiguously located blocks into a linear address space, changing affected control blocks to location offsets, and writing out the linked control blocks to DASD store. Upon the second pass, virtual addresses are substituted for the offsets upon rewriting of the control blocks to internal memory.

Claims

1. A method for relocating a set of linked control blocks stored on a persistent medium after a first pass and then, during second and subsequent passes, rewritten into an internal memory of a computing facility each time an application to which the control blocks are bound is executed, comprising the steps of:

(a) during the first pass,

path following through the set of control blocks which may be of different size and format using a path-following algorithm that takes into account the contents of each block;

coloring pointers to retain a history of the first time each specific path is followed through specific linked control blocks of the set to preclude further relocation of the same ones of the control blocks in each such path;

mapping, into a linear address space, discontiguously located ones of said blocks by changing the colored pointers to location offsets;

compressing said linked control blocks contiguously into the linear address space; and

writing the control blocks in compressed form to the persistent medium; and

(b) during second and subsequent passes, rewriting the control blocks to the internal memory from the persistent medium and substituting virtual addresses for the location offsets.

2. A method according to claim 1, wherein during said first pass, the step of mapping includes forming a directory for the linear address space that contains the compressed control blocks, said directory listing pointers requiring relocation.

3. A method according to claim 2, wherein the step of mapping includes calculating the offsets within the directory in a manner which maintains and preserves the path-following order upon rewriting of the stored linked control blocks from the persistent medium to internal memory during the second and subsequent passes.

4. A method according to claim 2, wherein the directory is appended to the linear address space.

5. A method according to claim 1, wherein the control blocks may be of different types, each type having a positionally different pointer location, and further including, during the coloring step, identifying the type of control block pointed to.

6. A method according to claim 1, wherein the linked control blocks comprise a network of heterogeneously linked blocks.