Implementation for collecting unmanaged memory

• US 20060259528A1
• Filed: 05/13/2005
• Published: 11/16/2006
• Est. Priority Date: 05/13/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Xie, Yin, Dussud, Cedric Patrick
• Granted Patent: US 7,707,232 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0276 Generational garbage collection
• CPC Class Codes: Y10S 707/99957 Garbage collection

Abstract

A method and system for garbage collecting managed and unmanaged memory that is no longer referenced. The time between allocations is compared with a threshold to determine if the garbage collector needs to collect unused memory. Unmanaged memory referenced by objects in the unused managed memory may be freed during the collection.

Claims

1. A computer-readable medium having computer-executable instructions, comprising:

storing a first time at which memory is allocated;

allocating additional memory at a second time;

determining a first elapsed time between the first and second times; and

if the first elapsed time is greater than or equal to a first threshold, causing a garbage collection of unreferenced memory blocks.

2. The computer-readable medium of claim 1, further comprising:

storing a third time at which a previous garbage collection occurred;

determining a second elapsed time between the first and third times; and

if the second elapsed time is greater than or equal to a second threshold, causing a garbage collection of unreferenced memory blocks.

3. The computer-readable medium of claim 1, wherein the memory comprises an object in managed memory that references a block of unmanaged memory, wherein the object takes much less memory of the managed memory than it references in the block it references in the unmanaged memory.

4. The computer-readable medium of claim 1, wherein storing a first time at which memory is allocated comprises storing the first time at which memory is allocated if the memory relates to an image.

5. The computer-readable medium of claim 1, wherein storing a first time at which memory is allocated comprises storing the first time at which memory is allocated if the allocation occurs shortly after another allocation.

6. The computer-readable medium of claim 1, wherein storing a first time at which memory is allocated occurs in response to a managed object calling a allocation monitor to report a size of unmanaged memory referenced by the managed object.

8. The computer-readable medium of claim 1, wherein the first threshold is one second.

9. The computer-readable medium of claim 1, wherein the first threshold is fixed at development time, tuned at runtime, or selectable at runtime.

7. The computer-readable medium, wherein the first threshold is larger than a time in which a computer having the memory can allocate memory for images.

10. In a computing environment, a method, comprising:

creating an image object in managed memory, wherein a garbage collector collects unused memory in the managed memory;

creating image data referenced by the object in unmanaged memory; and

performing a garbage collection based at least in part on a time between allocations of image objects in the managed memory.

11. The method of claim 10, wherein the unused memory comprises memory that was previously allocated for use by a program and that is no longer referenced by the program.

12. The method of claim 10, further comprising calling a finalizer method of the image object before collecting unused memory associated with the object, wherein the finalizer method returns the unmanaged memory referenced by the object to a free pool of memory.

13. The method of claim 10, further comprising updating a value that indicates how much unmanaged image data is associated with image objects in managed memory and not performing the garbage collection if the value is less than a memory threshold.

14. The method of claim 10, wherein the garbage collector comprises a generational garbage collector in which objects that are longer-lived are associated with generations and wherein the garbage collector collects unused memory associated with each subsequent generation at a lower frequency than its immediately prior generation.

15. The method of claim 10, wherein creating an image object in managed memory occurs in response to an application programming interface call to an API that provides enhanced graphics functionality.

16. In a computing environment, an apparatus, comprising:

a memory comprising a managed memory portion and an unmanaged memory portion;

a garbage collector arranged to collect unused memory from the unmanaged memory portion of the memory; and

an allocation monitor arranged to perform acts, comprising;

storing time data that indicates when memory is allocated for objects that reference data in the unmanaged memory and when a garbage collection occurs,

causing the garbage collector to perform an additional garbage collection based on the time data.

17. The apparatus of claim 16, wherein the time data comprises a prior time at which a most recent previous memory allocation occurred and a prior time at which a most recent previous garbage collection occurred.

18. The apparatus of claim 17, wherein causing the garbage collector to perform an additional garbage collection based on the time data comprises determining if an elapsed time between the prior time at which a most recent previous memory allocation occurred and a current time equals or exceeds an allocation threshold, and if so, causing the additional garbage collection to occur.

19. The apparatus of claim 17, wherein causing the garbage collector to perform an additional garbage collection based on the time data comprises determining if an elapsed time between the prior time at which a most recent previous garbage collection occurred and a current time equals or exceeds a collection threshold, and if so, causing the additional garbage collection to occur.