Garbage collection with memory quick release

• US 8,452,938 B1
• Filed: 04/08/2008
• Issued: 05/28/2013
• Est. Priority Date: 12/30/2004
• Status: Active Grant

• Current Assignee: Azul Systems Incorporated
• Original Assignee: Azul Systems Incorporated
• Inventors: Tene, Gil, Wolf, Michael A.
• Primary Examiner(s): PATEL, KAUSHIKKUMAR M
• Application Number:
  US12/082,238
• Time in Patent Office: 1,876 Days
• Field of Search: 711/203, 711/205
• US Class Current: 711/170
• CPC Class Codes: G06F 12/0253 Garbage collection, i.e. reclamation of unreferenced memory
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems

Abstract

Memory management includes identifying a region of virtual memory to be reclaimed, the region including at an object that is currently located at an original virtual memory location, and the region being supported by at least a portion of a memory resource; relocating the object from the original virtual memory location to a target virtual memory location; remapping one or more references to the object to the target virtual memory location; and releasing the portion of the memory resource prior to or contemporaneously with remapping the one or more references to the target location.

Claims

1. A method of memory management, comprising:

identifying a region of virtual memory to be reclaimed, the region including an object that is currently located at an original virtual memory location, and the region being supported by at least a portion of a memory resource;

relocating the object from the original virtual memory location to a target virtual memory location;

copying the object to the target virtual memory location;

establishing a forwarding pointer;

protecting the region of virtual memory to be reclaimed;

releasing the portion of the memory resource so that the portion of memory resource can be reused; and

after the portion of the memory resource is released, remapping one or more references to the object to the target virtual memory location.

2. The method of claim 1, wherein the region includes a page of virtual memory.

3. The method of claim 1, wherein remapping includes remapping all references to the object are remapped to the target location.

4. The method of claim 1, wherein the memory resource is physical memory.

5. The method of claim 1, wherein the object is a live object.

6. The method of claim 1, wherein the target virtual memory location is supported by another portion of the memory resource.

7. The method of claim 1, wherein the forwarding pointer is stored outside the region of virtual memory to be reclaimed.

8. The method of claim 1, wherein protecting the region of virtual memory to be reclaimed includes marking the region.

9. The method of claim 1, wherein a garbage collection barrier triggers in the event the object is accessed after the region is protected.

10. The method of claim 1, further comprising redirecting an operation that references the object to the target virtual memory location.

11. The method of claim 10, wherein redirecting the operation includes providing the forward pointer to the target virtual memory location.

12. A system comprising:

a memory resource;

a processor coupled to the memory resource, configured to;

identify a region of virtual memory to be reclaimed, the region including an object that is currently located at an original virtual memory location, and the region being supported by at least a portion of a memory resource;

copy the object to the target virtual memory location;

establish a forwarding pointer;

protect the region of virtual memory to be reclaimed;

relocate the object from the original virtual memory location to a target virtual memory location;

release the portion of the memory resource so that the portion of memory resource can be reused; and

after the portion of the memory resource is released, remap one or more references to the object to the target virtual memory location.

13. The system of claim 12, wherein the memory resource is physical memory.

14. The system of claim 12, wherein the object is a live object.

15. The system of claim 12, wherein the forwarding pointer is stored outside the region of virtual memory to be reclaimed.

16. The system of claim 12, wherein protecting the region of virtual memory to be reclaimed includes marking the region.

17. The system of claim 12, wherein a garbage collection barrier triggers in the event the object is accessed after the region is protected.

18. The system of claim 12, further comprising redirecting an operation that references the object to the target virtual memory location.

19. The system of claim 18, wherein redirecting the operation includes providing the forward pointer to the target virtual memory location.

20. A computer program product for memory management, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions configured for:

identifying a region of virtual memory to be reclaimed, the region including an object that is currently located at an original virtual memory location, and the region being supported by at least a portion of a memory resource;

relocating the object from the original virtual memory location to a target virtual memory location;

copying the object to the target virtual memory location;

establishing a forwarding pointer;

protecting the region of virtual memory to be reclaimed;

releasing the portion of the memory resource so that the portion of memory resource can be reused; and

after the portion of the memory resource is released, remapping one or more references to the object to the target virtual memory location.