SYSTEM AND METHODS FOR PRIORITIZING DATA IN A CACHE

• US 20150154216A1
• Filed: 12/22/2014
• Published: 06/04/2015
• Est. Priority Date: 10/18/2012
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Maybee, Mark, Week, Lisa
• Granted Patent: US 9,934,231 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 12/0897 with two or more cache hierarchy levels with multilevel cache hierarchies G06F12/0811
• 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 12/127 using additional replacement algorithms
• CPC Class Codes: G06F 16/172 Caching, prefetching or hoarding of files
• CPC Class Codes: G06F 16/1748 De-duplication implemented within the file system, e.g. based on file segments de-duplication techniques in storage systems for the management of data blocks G06F3/0641

Abstract

Implementations described and claimed herein provide a system and methods for prioritizing data in a cache. In one implementation, a priority level, such as critical, high, and normal, is assigned to cached data. The priority level dictates how long the data is cached and consequently, the order in which the data is evicted from the cache memory. Data assigned a priority level of critical will be resident in cache memory unless heavy memory pressure causes the system to reclaim memory and all data assigned a priority state of high or normal has been evicted. High priority data is cached longer than normal priority data, with normal priority data being evicted first. Accordingly, important data assigned a priority level of critical, such as a deduplication table, is kept resident in cache memory at the expense of other data, regardless of the frequency or recency of use of the data.

Claims

1. A method for prioritizing a retention of data comprising:

setting a maximum size of a critical state of a cache using at least one processor;

setting an upper limit on a size of a deduplication table using the at least one processor, the upper limit being less than the maximum size of the critical state;

storing an entirety of the deduplication table in the critical state of the cache; and

retaining the entirety of the deduplication table at the expense of data stored outside the critical state in the cache.

2. The method of claim 1, wherein data stored outside the critical state in the cache is stored in a plurality of states based on assigned priority.

3. The method of claim 2, wherein the plurality of states include a high priority state and a normal priority state.

4. The method of claim 3, wherein data stored in the normal priority state is evicted prior to data stored in the high priority state.

5. The method of claim 1, wherein the entirety of the deduplication table is retained at the expense of data stored outside the critical state in the cache by evicting the data stored outside the critical state in the cache based on a cache replacement policy.

6. The method of claim 5, wherein the cache replacement policy comprises evicting data based on at least one of:

recency of use or frequency of use.

7. The method of claim 1, wherein space in the cache for data stored outside the critical state is dynamically adjusted based on a current size of the critical state.

8. One or more non-transitory tangible computer-readable storage media storing computer-executable instructions for performing a computer process on a computing system, the computer process comprising:

receiving a write request to write data to a cache having a plurality of states, the data assigned a priority level, the plurality of states including a critical state and a non-critical state;

determining a current size of the critical state compared to a maximum side of the critical state, the maximum size being less than a total size of the cache;

writing the data to one of the plurality of states based on the priority level and the current size of the critical state; and

dynamically adjusting a size of the non-critical state based on an updated size of the critical state after the data is written to one or the plurality of states.

9. The one or more non-transitory tangible computer-readable storage media of claim 8, wherein the maximum size of the critical state is greater than an upper limit of a deduplication table.

10. The one or more non-transitory tangible computer-readable storage media of claim 8, wherein the size of the non-critical state is increased where the updated size of the critical state is equal to the current size of the critical state and a size of the plurality of states is less than the maximum size of the critical state.

11. The one or more non-transitory tangible computer-readable storage media of claim 8, wherein the size of the non-critical state is decreased where the updated size of the critical state is greater than the current size of the critical state, the size of the non-critical state being decreased by evicting data stored in the non-critical state based on a cache replacement policy.

12. The one or more non-transitory tangible computer-readable storage media of claim 11, wherein the cache replacement policy includes evicting data based on at least one of:

recency of use or frequency of use.

13. The one or more non-transitory tangible computer-readable storage media of claim 8, wherein the non-critical state includes a high priority state and a normal priority state.

14. The one or more non-transitory tangible computer-readable storage media of claim 13, wherein the size of the non-critical state is dynamically adjusted by evicting data from the normal priority state.

15. The one or more non-transitory tangible computer-readable storage media of claim 13, wherein the size of the non-critical state is dynamically adjusted by evicting data from the high priority state where no data is stored in the normal priority state.

16. The one or more non-transitory tangible computer-readable storage media of claim 8, wherein the data is not written to the cache where the priority level is non-critical and a difference between the current size of the critical state and the maximum size of the critical state is less than a size of the data.

17. A system for prioritizing a retention of data comprising:

a cache having a critical state and a non-critical state, the critical state configured to grow unbounded until a maximum size of the critical state is reached by dynamically adjusting the non-critical state, the maximum size of the critical state being less than a total size of the cache and greater than an upper limit of a deduplication table, the non-critical state dynamically adjusted based on one or more priority levels assigned to data stored in the non-critical state.

18. The system of claim 17, wherein the one or more priority levels includes at least one of normal or high.

19. The system of claim 18, wherein the non-critical state is dynamically adjusted by evicting data assigned the normal priority level prior to data assigned the high priority level.

20. The system of claim 17, wherein the one or more priority levels are assigned based on at least one of:

recency of use or frequency of use.