Methods for dynamically resizing memory pools

• US 7,469,329 B2
• Filed: 03/30/2006
• Issued: 12/23/2008
• Est. Priority Date: 03/30/2006
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lightstone, Sam Sampson, Garcia-Arellano, Christian Marcelo, Kuczynski, Wojciech, Storm, Adam J., Zheng, Roger Luo Quan, Posner, Sarah
• Primary Examiner(s): Kim; Matt
• Assistant Examiner(s): PATEL, HETUL B
• Application Number:
  US11/278,133
• Publication Number:
  US 20070233990A1
• Time in Patent Office: 999 Days
• Field of Search: 711/170
• 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 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, wherein each page of the at least one page groupings comprises a plurality of memory blocks;

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

iv) if no page grouping that is available to be freed from the memory pool is identified in iii), then copying all used memory blocks from each page grouping in a candidate list of at least one page grouping having at least one used memory blocks, to another page grouping in order to free each page grouping in the candidate list, of used memory blocks,

wherein if an interrupt occurs in iv) to cancel the decrease in allocation, the decrease in allocation is canceled,

wherein if an interrupt occurs in iv) to further decrease allocation to the memory pool, at least one additional page grouping is added to the candidate list, and

wherein if an interrupt occurs in iv) to further increase allocation to the memory pool, at least one page grouping is removed from the candidate list.

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

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

3. The data processing system implemented method of claim 1, further comprising identifying the candidate list of at least one page grouping that are available to be freed from the memory pool based on the amount of free memory blocks in the at least one 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 each memory block 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 list of at least one 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 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, wherein the list of page groupings are sorted according to a number of unused memory blocks.

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.