Integration of the frequency of usage of tracks in a tiered storage system into a cache management system of a storage controller

• US 10,691,596 B2
• Filed: 04/27/2018
• Issued: 06/23/2020
• Est. Priority Date: 04/27/2018
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gupta, Lokesh M., Borlick, Matthew G., Anderson, Kyle A., Ash, Kevin J.
• Primary Examiner(s): Farrokh, Hashem
• Application Number:
  US15/964,904
• Publication Number:
  US 20190332535A1
• Time in Patent Office: 788 Days
• Field of Search: 711101
• CPC Class Codes: G06F 12/0811 with multilevel cache hierarchies
• CPC Class Codes: G06F 12/123 with age lists, e.g. queue, most recently used [MRU] list or least recently used [LRU] list
• CPC Class Codes: G06F 2212/1024 Latency reduction
• CPC Class Codes: G06F 2212/608 Details relating to cache mapping
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0649 Lifecycle management
• CPC Class Codes: G06F 3/0685 Hybrid storage combining heterogeneous device types, e.g. hierarchical storage, hybrid arrays

Abstract

A storage tier management application indicates a heat index for each extent of a plurality of extents, wherein a higher heat index indicates a greater frequency of usage of tracks of an extent than a lower heat index. A least recently used (LRU) list for cache management is configured to perform demotion of tracks of a lower heat index prior to demotion of tracks of a higher heat index.

Claims

1. A method, comprising:

maintaining, by a cache management application, a cache for a storage controller and a list corresponding to tracks in the cache, wherein the cache management application places tracks in the list by measuring frequency of usage of tracks in a first time period;

maintaining, by a storage tier management application, a plurality of storage tiers controlled by the storage controller, wherein the storage tier management application collects usage statistics of tracks over a second time period;

maintaining, by the cache management application, in the list, a plurality of partitions, wherein each partition of the plurality of partitions is comprised of a plurality of tracks, and wherein each partition of the plurality of partitions represents a heat index range;

adding, by the cache management application, a new track to the list by;

determining a heat index of the new track as indicated by the storage tier management application; and

including the new track in a partition of the plurality of partitions whose heat index range encompasses the heat index of the new track; and

demoting, by the cache management application, a track from the list to discard the track from the cache by;

determining which partition of the plurality of partitions has a heat index range that encompasses lowest heat indexes;

determining whether the determined partition has one or more tracks;

in response to determining that the determined partition has one or more tracks, demoting a least recently used (LRU) track of the determined partition; and

in response to determining that the determined partition does not have one or more tracks, determining a new partition of the plurality of partitions that has a heat index range that encompasses next lowest heat indexes for demoting one or more additional tracks from the list.

2. The method of claim 1, wherein the second time period is at least a 100 times greater than the first time period.

3. The method of claim 2, wherein the storage tier management application periodically moves extents of a lower heat index to a storage device having a higher response time and moves extents of higher heat index to a storage device having a lower response time.

4. The method of claim 1, wherein the heat index of the new track is an indication of a frequency of usage of tracks of an extent that includes the new track as determined by the storage tier management application.

5. The method of claim 1, wherein the second time period is greater than the first time period.

6. The method of claim 1, wherein the first time period is at most 10 minutes, and wherein the second time period is at least 1 hour.

7. A system, comprising:

a memory; and

a processor coupled to the memory, wherein the processor performs operations, the operations performed by the processor comprising;

maintaining, by a cache management application, a cache and a list corresponding to tracks in the cache, wherein the cache management application places tracks in the list by measuring frequency of usage of tracks in a first time period;

maintaining, by a storage tier management application, a plurality of storage tiers, wherein the storage tier management application collects usage statistics of tracks over a second time period;

maintaining, by the cache management application, in the list, a plurality of partitions, wherein each partition of the plurality of partitions is comprised of a plurality of tracks, and wherein each partition of the plurality of partitions represents a heat index range;

adding, by the cache management application, a new track to the list by;

determining a heat index of the new track as indicated by the storage tier management application; and

including the new track in a partition of the plurality of partitions whose heat index range encompasses the heat index of the new track; and

demoting, by the cache management application, a track from the list to discard the track from the cache by;

determining which partition of the plurality of partitions has a heat index range that encompasses lowest heat indexes;

determining whether the determined partition has one or more tracks;

in response to determining that the determined partition has one or more tracks, demoting a least recently used (LRU) track of the determined partition; and

in response to determining that the determined partition does not have one or more tracks, determining a new partition of the plurality of partitions that has a heat index range that encompasses next lowest heat indexes for demoting one or more additional tracks from the list.

8. The system of claim 7, wherein, wherein the second time period is at least a 100 times greater than the first time period.

9. The system of claim 8, wherein the storage tier management application periodically moves extents of a lower heat index to a storage device having a higher response time and moves extents of higher heat index to a storage device having a lower response time.

10. The system of claim 7, wherein the heat index of the new track is an indication of a frequency of usage of tracks of an extent that includes the new track as determined by the storage tier management application.

11. The system of claim 7, wherein the second time period is greater than the first time period.

12. The system of claim 7, wherein the first time period is at most 10 minutes, and wherein the second time period is at least 1 hour.

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 configured to perform operations, the operations comprising:

maintaining, by a cache management application, a cache for a storage controller and a list corresponding to tracks in the cache, wherein the cache management application places tracks in the list by measuring frequency of usage of tracks in a first time period;

maintaining, by a storage tier management application, a plurality of storage tiers controlled by the storage controller, wherein the storage tier management application collects usage statistics of tracks over a second time period;

maintaining, by the cache management application, in the list, a plurality of partitions, wherein each partition of the plurality of partitions is comprised of a plurality of tracks, and wherein each partition of the plurality of partitions represents a heat index range;

adding, by the cache management application, a new track to the list by;

determining a heat index of the new track as indicated by the storage tier management application; and

including the new track in a partition of the plurality of partitions whose heat index range encompasses the heat index of the new track; and

demoting, by the cache management application, a track from the list to discard the track from the cache by;

determining which partition of the plurality of partitions has a heat index range that encompasses lowest heat indexes;

determining whether the determined partition has one or more tracks;

in response to determining that the determined partition has one or more tracks, demoting a least recently used (LRU) track of the determined partition; and

in response to determining that the determined partition does not have one or more tracks, determining a new partition of the plurality of partitions that has a heat index range that encompasses next lowest heat indexes for demoting one or more additional tracks from the list.

14. The computer program product of claim 13, wherein the second time period is at least a 100 times greater than the first time period.

15. The computer program product of claim 14, wherein the storage tier management application periodically moves extents of a lower heat index to a storage device having a higher response time and moves extents of higher heat index to a storage device having a lower response time.

16. The computer program product of claim 13, wherein the heat index of the new track is an indication of a frequency of usage of tracks of an extent that includes the new track as determined by the storage tier management application.

17. The computer program product of claim 13, wherein the second time period is greater than the first time period.

18. The computer program product of claim 13, wherein the first time period is at most 10 minutes, and wherein the second time period is at least 1 hour.