SYSTEMS AND METHODS FOR DYNAMICALLY RESIZING MEMORY POOLS

• US 20070233990A1
• Filed: 03/30/2006
• Published: 10/04/2007
• Est. Priority Date: 03/30/2006
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kuczynski, Wojciech, Lightstone, Sam, Storm, Adam, Posner, Sarah, Garcia-Arellano, Christian, Zheng, Roger
• Granted Patent: US 7,469,329 B2
• Time in Patent Office: Days
• US Class Current: 711/170
• CPC Class Codes: G06F 16/22 Indexing; Data structures therefor; Storage structures
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

There are disclosed systems, computer program products, and methods for dynamically resizing memory pools used by database management systems. In one aspect, if a decrease in allocation to the memory pool is required, at least one page grouping that may be freed from the memory pool is identified as a candidate based on its position in a list of page groupings. If the page grouping contains any used memory blocks, the used memory blocks may be copied from a candidate page grouping to another page grouping in the list in order to free the candidate page grouping. Once the candidate page grouping is free of used memory blocks, the candidate page grouping may be freed from the memory pool. As an example, this method may be used for dynamically resizing locklists or lock memory.

Claims

1. A data processing system implemented method for resizing a memory pool in a database management system, comprising:

i) forming the memory pool from at least one page grouping;

ii) if an increase in allocation to the memory pool is required, adding at least one page grouping to the memory pool to form a chain of page groupings;

iii) if a decrease in allocation to the memory pool is required, identifying at least one page grouping free of used memory blocks that may be freed from the memory pool, and freeing the at least one page grouping from the memory pool.

2. The data processing system implemented method of claim 1, further comprising:

iv) if no page groupings that may be freed from the memory pool are identified in iii), then copying used memory blocks from a candidate page grouping to another page grouping in order to free the candidate page grouping of used memory blocks;

v) once the candidate page grouping is free of used memory blocks, freeing the candidate page grouping from the memory pool.

3. The data processing system implemented method of claim 2, further comprising identifying a candidate page grouping that may be freed from the memory pool based on the amount of free memory blocks in the page grouping.

4. The data processing system implemented method of claim 3, wherein each page grouping comprises a plurality of pages each including a page header pointing to a page grouping control block associated with the page grouping, and each page grouping control block contains information about whether memory blocks in the page grouping are free or used, and the method further comprises accessing the page grouping control block to determine the location of free memory blocks in the page grouping.

5. The data processing system implemented method of claim 4, further comprising organizing the page groupings into a list of page groupings based on the amount of free memory blocks in each page grouping, and identifying the candidate page grouping for freeing based on its order in the list of page groupings.

6. The data processing system implemented method of claim 5, further comprising preferentially using memory blocks from a page grouping based on its position in the list of page groupings such that memory blocks are used from fewer page groupings, whereby fragmentation of used memory blocks amongst the page groupings is decreased.

7. The data processing system implemented method of claim 6, wherein the memory pool is a locklist, and the memory block is a lock request block in the locklist.

8. A data processing system for resizing a memory pool in a database management system, comprising:

means for forming the memory pool from at least one page grouping;

means for adding at least one page grouping to the memory pool to form a chain of page groupings if an increase in allocation of memory to the memory pool is required;

means for identifying at least one page grouping free of used memory blocks that may be freed from the memory pool, and freeing the at least one page grouping from the memory pool if a decrease in allocation of memory to the memory pool is required.

9. The data processing system of claim 8, further comprising:

means for copying used memory blocks from a candidate page grouping to another page grouping in order to free the candidate page grouping of used memory blocks;

means for freeing the candidate page grouping from the memory pool once the candidate page grouping is free of used memory blocks.

10. The data processing system of claim 9, further comprising means for identifying a candidate page grouping that may be freed from the memory pool based on the amount of free memory blocks in the page grouping.

11. The data processing system of claim 10, wherein each page grouping comprises a plurality of pages each including a page header pointing to a page grouping control block associated with the page grouping, and each page grouping control block contains information about whether memory blocks in the page grouping are free or used, and the system further comprises means for accessing the page grouping control block to determine the location of free memory blocks in the page grouping.

12. The data processing system of claim 11, further comprising means for organizing the page groupings into a list of page groupings based on the amount of free memory blocks in each page grouping, and identifying a candidate page grouping for freeing based on the order of page groupings in the list of page groupings.

13. The data processing system of claim 12, further comprising means for preferentially using memory blocks from a page grouping based on its position in the list of page groupings such that memory blocks are used from fewer page groupings, whereby fragmentation of used memory blocks amongst the page groupings is decreased.

14. The data processing system of claim 13, wherein the memory pool is a locklist, and the memory block is a lock request block in the locklist.

15. A computer program product comprising a data processor readable medium storing code that, when loaded into a data processing device, adapts the device to resize a memory pool, the data processor readable medium including:

code for forming the memory pool from at least one page grouping;

code for adding at least one page grouping to the memory pool to form a chain of page groupings if an increase in allocation of memory to the memory pool is required;

code for identifying at least one page grouping free of used memory blocks that may be freed from the memory pool, and freeing the at least one page grouping from the memory pool if a decrease in allocation of memory to the memory pool is required.

16. The computer program product of claim 15, wherein the data processor readable medium further includes:

code for copying used memory blocks from a candidate page grouping to another page grouping in order to free the candidate page grouping of used memory blocks;

code for freeing the candidate page grouping from the memory pool once the candidate page grouping is free of used memory blocks.

17. The computer program product of claim 16, wherein the data processor readable medium further includes code for identifying a candidate page grouping that may be freed from the memory pool based on the amount of free memory blocks in the page grouping.

18. The computer program product of claim 17, wherein each page grouping comprises a plurality of pages each including a page header pointing to a page grouping control block associated with the page grouping, and each page grouping control block contains information about whether memory blocks in the page grouping are free or used, and the data processor readable medium further includes code for accessing the page grouping control block to determine the location of free memory blocks in the page grouping.

19. The computer program product of claim 18, wherein the data processor readable medium further includes code for organizing the page groupings into a list of page groupings based on the amount of free memory blocks in the page grouping, and identifying a candidate page grouping for freeing based on the order of page groupings in the list of page groupings.

20. The computer program product of claim 19, wherein the data processor readable medium further includes code for preferentially using memory blocks from a page grouping based on its position in the list of page groupings such that memory blocks are used from fewer page groupings, whereby fragmentation of used memory blocks amongst the page groupings is decreased.

21. The computer program product of claim 20, wherein the memory pool is a locklist, and the memory block is a lock request block in the locklist.