Dynamically controlling a file system write cache

Patent metadata

Field	Value
Publication number	US-9542328-B2
Application number	US-201514605665-A
Country	US
Kind code	B2
Filing date	Jan 26, 2015
Priority date	Jan 26, 2015
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

Methods, computing systems and computer program products implement embodiments of the present invention that include initializing, by a processor executing a file system in communication with a block manager managing multiple storage regions on a storage device, a file system write cache to have a default cache size, the default cache size corresponding to a first storage capacity of a default number of the storage regions. Upon detecting that a current number of the storage regions that are not in use by the block manager is less than the default number, the file system write cache is resized to a reduced cache size that corresponds to a second storage capacity of the current number of the storage regions. While the file system write cache has the reduced cache size, the file system write cache can be resized back to the default cache size as unused storage regions become available.

First claim

The invention claimed is:

1. A method, comprising:
initializing, by a processor executing a file system in communication with a block manager managing multiple storage regions on a storage device, a file system write cache to have a default cache size, the default cache size corresponding to a first storage capacity of a default number of the storage regions;
determining a current number of the storage regions that are not in use by the block manager;
upon detecting that the current number is less than the default number, resizing the file system write cache to a reduced cache size that corresponds to a second storage capacity of the current number of the storage regions; and
determining, while the file system write cache has the reduced cache size, a subsequent number of the storage regions that are not in use by the file system, and upon detecting that the subsequent number is greater than the current number, resizing the file system write cache to an expanded cache size that corresponds to a third storage capacity comprising a lesser of the subsequent number of the storage regions and the first storage capacity.

2. The method according to claim 1 , wherein initializing the file system write cache comprises defining, on the storage device, a reserved file comprising the default number of the storage regions.

3. The message according to claim 2 , wherein detecting that the current number of the storage regions is less than the default number comprises attempting, by the file system, a data destage to the block manager, and receiving, from the block manager, an insufficient space error in response to the data destage attempt.

4. The message according to claim 3 , and comprising upon resizing the file system write cache to the reduced cache size, borrowing, by the file system, one or more of the storage regions in the reserved file in order to complete the data destage.

5. The method according to claim 4 , and comprising upon resizing the file system write cache to an expanded cache size, adding one or more of the storage regions to the reserved file, thereby resizing the file to the third storage capacity.

6. The method according to claim 5 , and comprising releasing, by the file system, one or more of the multiple storage regions, and performing an operation selected from a list consisting of adding the one or more released storage regions to the reserved file and conveying a notification to the block manager indicating the release.

7. An apparatus, comprising:
a storage device;
a memory configured to store a file system write cache; and
a processor configured:
to execute a block manager configured to manage multiple storage regions on the storage device; and
to execute a file system manager configured:
to initialize the file system write cache to have a default cache size, the default cache size corresponding to a first storage capacity of a default number of the storage regions;
to determine a current number of the storage regions that are not in use by the block manager;
upon detecting that the current number is less than the default number, to resize the file system write cache to a reduced cache size that corresponds to a second storage capacity of the current number of the storage regions; and
to determine, while the file system write cache has the reduced cache size, a subsequent number of the storage regions that are not in use by the file system, and upon detecting that the subsequent number is greater than the current number, to resize the file system write cache to an expanded cache size that corresponds to a third storage capacity comprising a lesser of the subsequent number of the storage regions and the first storage capacity.

8. The apparatus according to claim 7 , wherein the processor is configured to initialize the file system write cache by defining, on the storage device, a reserved file comprising the default number of the storage regions.

9. The apparatus according to claim 8 , wherein the processor is configured to detect that the current number of the storage regions is less than the default number by attempting, by the file system, a data destage to the block manager, and receiving, from the block manager, an insufficient space error in response to the data destage attempt.

10. The apparatus according to claim 9 , wherein upon resizing the file system write cache to the reduced cache size, the processor is configured to borrow one or more of the storage regions in the reserved file in order to complete the data destage.

11. The apparatus according to claim 10 , wherein upon resizing the file system write cache to an expanded cache size, the processor is configured to add one or more of the storage regions to the reserved file, thereby resizing the file to the third storage capacity.

12. The apparatus according to claim 11 , wherein the processor is configured to release one or more of the multiple storage regions, and to perform an operation selected from a list consisting of adding the one or more released storage regions to the reserved file and conveying a notification to the block manager indicating the release.

13. A computer program product, the computer program product comprising:
a non-transitory computer readable storage medium having computer readable program code embodied therewith, the computer readable program code comprising:
computer readable program code configured to initialize, by a processor executing a file system in communication with a block manager managing multiple storage regions on a storage device, a file system write cache to have a default cache size, the default cache size corresponding to a first storage capacity of a default number of the storage regions;
computer readable program code configured to determine a current number of the storage regions that are not in use by the block manager;
computer readable program code configured upon detecting that the current number is less than the default number, to resize the file system write cache to a reduced cache size that corresponds to a second storage capacity of the current number of the storage regions; and
computer readable program code configured to determine, while the file system write cache has the reduced cache size, a subsequent number of the storage regions that are not in use by the file system, and upon detecting that the subsequent number is greater than the current number, to resize the file system write cache to an expanded cache size that corresponds to a third storage capacity comprising a lesser of the subsequent number of the storage regions and the first storage capacity.

14. The computer program product according to claim 13 , wherein the computer readable program code is configured to initialize the file system write cache by defining, on the storage device, a reserved file comprising the default number of the storage regions.

15. The computer program product according to claim 14 , wherein the computer readable program code is configured to detect that the current number of the storage regions is less than the default number by attempting, by the file system, a data destage to the block manager, and receiving, from the block manager, an insufficient space error in response to the data destage attempt.

16. The computer program product according to claim 15 , and comprising computer readable program code configured, upon resizing the file system write cache to the reduced cache size, to borrow, by the file system, one or more of the storage regions in the reserved file in order to complete the data destage.

17. The computer program product acc

Assignees

• IBM

Inventors

• Chen Lior
• Kalaev Maxim
• Margalit Amit
• Matosevich Rivka M

Classifications

• G06F12/0871 Primary

  Allocation or management of cache space · CPC title

• G06F2212/62

  Details of cache specific to multiprocessor cache arrangements · CPC title

• G06F12/12

  Replacement control · CPC title

• G06F12/0833

  in combination with broadcast means (e.g. for invalidation or updating) · CPC title

• G06F12/1009

  using page tables, e.g. page table structures · CPC title