METHODS AND SYSTEMS FOR DEADLOCK-FREE ALLOCATION OF MEMORY

• US 20100042755A1
• Filed: 08/15/2008
• Published: 02/18/2010
• Est. Priority Date: 08/15/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: SCALES, William J., FUENTE, Carlos F.
• Granted Patent: US 8,028,113 B2
• Time in Patent Office: Days
• US Class Current: 710/22
• CPC Class Codes: G06F 13/28 using burst mode transfer, e.g. direct memory access DMA, cycle steal G06F13/32 takes precedence

Abstract

Methods and systems for memory management. A method for memory management includes: maintaining a reference count for at least one first process associated with a portion of memory; maintaining a shared reference count for at least one second process associated with the portion of memory; and freeing the portion of memory when the shared reference count is decremented to zero.

Claims

1. A method for memory management, comprising:

maintaining a reference count for at least one first process associated with a portion of memory;

maintaining a shared reference count for at least one second process associated with the portion of memory; and

freeing the portion of memory when the shared reference count is decremented to zero and the reference count equals zero.

2. The method of claim 1, wherein the at least one first process comprises an updating process.

3. The method of claim 2, wherein the at least one second process comprises a non-updating process.

4. The method of claim 1, wherein the reference count and the shared reference count are maintained by a storage controller.

5. The method of claim 4, wherein:

the portion of memory is a page, and

the reference count and the shared reference count are maintained in a page table.

6. The method of claim 4, further comprising using the portion of memory in direct memory access operations.

7. The method of claim 1, wherein the freeing occurs after a merging operation.

8. A system for allocating memory resources, comprising:

a storage controller including hardware and software arranged to;

designate I/O processes as one of updating processes and non-updating processes;

maintain a reference count of the updating processes and a shared reference count of the non-updating processes associated with a page of memory; and

delay freeing the page until the shared reference count equals zero.

9. The system of claim 8, wherein the storage controller comprises non-volatile memory.

10. The system of claim 8, wherein the storage controller comprises at least one hardware interface for connecting to one of a host and a disk.

11. The system of claim 8, wherein the storage controller comprises:

a memory manager;

a cache directory;

a host I/O component; and

a disk I/O component.

12. The system of claim 8, wherein the reference count is based upon the updating processes associated with the page.

13. The system of claim 12, wherein the shared reference count is based upon the non-updating processes associated with the page.

14. A computer program product comprising a tangible computer-usable medium having a computer readable program embodied in the medium, wherein the computer readable program when executed on a storage controller causes the storage controller to:

receive a first function call associated with a first process;

designate the first process as a non-updating process;

allocate to the first process a first page reference to a first page of memory;

receive a second function call associated with a second process;

designate the second process as an updating process;

copy contents of the first page to a second page;

merge sectors of the first page to the second page after the second process has altered sectors of the second page; and

delay freeing the first page until the first process terminates.

15. The computer program product of claim 14, wherein the delaying comprises:

maintaining a reference count and a shared reference count associated with the first page; and

freeing the first page when the shared reference count equals zero.

16. The computer program product of claim 15, wherein the shared reference count represents a number of non-updating processes accessing the first page.

17. The computer program product of claim 15, wherein the reference count and the shared reference count are maintained in a data structure.

18. The computer program product of claim 17, wherein the data structure comprises a page table.

19. The computer program product of claim 15, wherein the computer readable program further causes the storage controller to:

increment the shared reference count when a new non-updating process accesses the first page; and

decrement the shared reference count when an existing non-updating process terminates.

20. A method for managing memory, comprising:

providing a direct memory access storage controller that operates to;

designate I/O processes associated with a page of memory as one of updating and non-updating;

update a reference count representing a number of updating processes associated with the page;

update a shared reference count representing a total number of non-updating processes associated with the page; and

free the page for use by other code when the shared reference count decrements to zero,

wherein the storage controller comprises a combination of hardware and software.