Method and apparatus for reclaiming memory from a heap

• US 20060253498A1
• Filed: 05/05/2005
• Published: 11/09/2006
• Est. Priority Date: 05/05/2005
• Status: Abandoned Application

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Williamson, Paul Stuart, Brown, Michael Wayne, Barrs, John William
• Application Number:
  US11/122,695
• Publication Number:
  US 20060253498A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0269 Incremental or concurrent garbage collection, e.g. in real-time systems G06F12/0261 takes precedence
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems

Abstract

An improved method, apparatus, and computer instructions for managing a heap. Live objects in portions of space in the heap are marked in response to a request to reclaim space in the heap. The portions of space are moved into a virtual memory in response to marking the live objects. The old objects are removed from the portions of space in the heap in the virtual memory.

Claims

1. A method in a data processing system for managing a heap, the method comprising:

responsive to a request to reclaim space in the heap, marking live objects in portions of space in the heap;

responsive to marking the live objects, moving the portions of space into a virtual memory; and

removing old objects from the portions of space in the heap in the virtual memory.

2. The method of claim 1, wherein the removing step is performed by sweeping the portions of the space in the heap in the virtual memory.

3. The method of claim 1, wherein the portions of space is all of the space in the heap.

4. The method of claim 1, wherein the portions of space in the heap in the virtual memory are stored in a swap file.

5. The method of claim 1 further comprising:

responsive to an object in the portions of space in the heap in the virtual memory being referenced, swapping the object back into the heap.

6. The method of claim 1, wherein the removing step is performed as part of a sweep phase in performing garbage collection on the portions of space in the heap in virtual memory.

7. The method of claim 1, wherein the removing step is performed as a background operation.

8. The method of claim 1, wherein the removing step includes:

storing the old objects in a persistent storage.

9. The method of claim 1 further comprising:

receiving the request from an application.

10. The method of claim 1, wherein the portions of the heap have a selected address range.

11. The method of claim 1, wherein the marking step comprises:

moving a live object in the heap to a selected address based on an age of the object.

12. The method of claim 1, wherein the marking step comprises:

associating a time stamp with a live-object.

13. The method of claim 1, wherein the marking step comprises:

marking bit masks associated with the live objects, wherein the bit masks are used to identify old objects in the heap.

14. The method of claim 1, wherein an age of an object is stored in a call stack.

15. The method of claim 1, wherein an identification of objects is stored in entries in a data structure containing delta data or the objects and wherein the entries are sorted by age and indicates a range of entries for number of objects stored in persistent storage.

16. A computer program product in a data processing system for managing a heap, the computer program product comprising:

first instructions, responsive to a request to reclaim space in the heap, for marking live objects in portions of space in the heap;

second instructions, responsive to marking the live objects, for moving the portions of space into a virtual memory; and

third instructions for removing old objects from the portions of space in the heap in the virtual memory.

17. The computer program product of claim 16 further comprising:

fourth instructions for receiving the request from an application.

18. The computer program product of claim 16, wherein the first instructions comprises:

sub instructions for marking bit masks associated with the live objects, wherein the bit masks are used to identify old objects in the heap.

19. The computer program product of claim 16, wherein the portions of space in the heap in the virtual memory are stored in a swap file.

20. A data processing system comprising:

a bus;

a communications unit connected to the bus;

a memory connected to the bus, wherein the memory includes a set of instructions; and

a processor unit connected to the bus, wherein the processor unit executes the set of instructions to manage a heap;

mark live objects in portions of space in the heap in response to a request to reclaim space in the heap;

move the portions of space into a virtual memory in response to marking the live objects; and

remove old objects from the portions of space in the heap in the virtual memory.