Writing cached data forward on read

• US 8,825,937 B2
• Filed: 02/25/2013
• Issued: 09/02/2014
• Est. Priority Date: 02/25/2011
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Fusion-IO Incorporated (Western Digital Corporation)
• Inventors: Atkisson, David, Flynn, David
• Primary Examiner(s): Thai, Tuan
• Assistant Examiner(s): Waddy, Jr., Edward
• Application Number:
  US13/776,406
• Publication Number:
  US 20130166816A1
• Time in Patent Office: 554 Days
• Field of Search: 711/133, 711/102, 711/118, 711/E12.026, 711/122, 711/E12.024, 711/103, 711/E12.008, 711/143, 711/E12.002, 711/E12.021, 711/E12.043, 711/113, 711/E12.041, 711/E12.084, 711/165
• US Class Current: 711/102
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0802 Addressing of a memory level in which the access to the desired data or data block requires associative addressing means, e.g. caches
• CPC Class Codes: G06F 12/0895 of parts of caches, e.g. directory or tag array
• CPC Class Codes: G06F 12/126 with special data handling, e.g. priority of data or instructions, handling errors or pinning
• CPC Class Codes: G06F 2212/601 Reconfiguration of cache memory

Abstract

Apparatuses, systems, and methods are disclosed for managing contents of a cache. A method includes receiving a read request for data stored in a non-volatile cache. A method includes determining whether a read request satisfies a frequent read threshold for a cache. A method includes writing data of a read request forward on a sequential log-based writing structure of a cache in response to determining that the read request satisfies a frequent read threshold.

Claims

1. A method for managing contents of a cache, the method comprising:

receiving a read request for data stored in a non-volatile cache;

reading the data of the read request from a sequential log-based writing structure of the cache into volatile memory to service the read request;

determining whether the read request satisfies a frequent read threshold for the cache; and

writing the data of the read request forward on the sequential log-based writing structure from the volatile memory without re-reading the data of the read request from a non-volatile storage medium of the cache in response to determining that the read request satisfies the frequent read threshold.

2. The method of claim 1, further comprising invalidating a previous version of the data in the sequential log-based writing structure of the non-volatile cache in response to writing the data forward on the sequential log-based writing structure.

3. The method of claim 1, further comprising transitioning the data of the read request from a recent read pool to a frequent read pool in response to determining that the read request satisfies the frequent read threshold.

4. The method of claim 1, further comprising buffering the data of the read request with other data satisfying the frequent read threshold in a storage region and writing the storage region of the buffered data forward on the sequential log-based writing structure in response to filling the storage region.

5. The method of claim 1, wherein writing the data of the read request forward comprises combining data of the read request with data queued to be written to the non-volatile storage medium and writing the combined data to an append point of the sequential log-based writing structure.

6. The method of claim 1, wherein writing the data of the read request forward comprises appending the data of the read request to a separate append point of the sequential log-based writing structure, the separate append point associated with data satisfying the frequent read threshold.

7. The method of claim 1, wherein writing the data of the read request forward comprises writing the data of the read request to a separate sequential log-based writing structure, the separate sequential log-based writing structure associated with data satisfying the frequent read threshold.

8. The method of claim 7, further comprising recovering storage capacity from the separate sequential log-based writing structure less frequently than from an ingestion sequential log-based writing structure.

9. The method of claim 7, wherein the data of the read request is written to one of a plurality of separate sequential log-based writing structures based on a read request frequency count for the data of the read request such that the plurality of separate sequential log-based writing structures are grouped based on frequency of access.

10. The method of claim 1, wherein in response to writing forward frequently accessed data from a storage region, the storage region comprises solely evictable data such that a storage recovery process recovers the storage region without relocating data of the storage region.

11. The method of claim 1, wherein the volatile memory comprises volatile memory of a host device in communication with the non-volatile cache.

12. An apparatus for managing contents of a cache, the apparatus comprising:

a read request module configured to cause data stored in a non-volatile storage medium of a cache to be read from a sequential log-based writing structure of the cache into volatile memory in response to a read request for the data;

a read pool module configured to determine whether the read request satisfies a frequent read threshold; and

a write forward module configured to write the data forward from the volatile memory to an append point of the sequential log-based writing structure of the cache without an additional read transaction with the non-volatile storage medium of the cache in response to the read pool module determining that the read request satisfies the frequent read threshold.

13. The apparatus of claim 12, wherein the write forward module is configured to cause the data of the read request to be copied to one of a plurality of separate sequential log-based writing structures of the cache, the one of the plurality of separate sequential log-based writing structures selected based on a read request frequency count for the data of the read request.

14. A computing system having a memory and one or more processors for managing contents of a cache, the computing system comprising:

a storage controller for a non-volatile solid-state storage device, the non-volatile solid-state storage device in communication with a processor over one or more communications buses;

a cache controller in communication with the storage controller, the cache controller comprising,

a storage request module configured to monitor read requests received for the cache controller;

a read request module configured to cause data stored in a non-volatile storage medium of the solid-state storage device to be read from a sequential log-based writing structure of the non-volatile storage medium into volatile memory in response to the storage request module monitoring a read request for the data, the data read into the volatile memory to service the read request;

a read pool module configured to determine whether the read request satisfies a frequent read threshold; and

a write forward module configured to cause the data of the read request to be written forward on the sequential log-based writing structure from the volatile memory without an additional read transaction with the non-volatile storage medium in response to the read pool module determining that the read request satisfies the frequent read threshold.

15. The computing system of claim 14, further comprising a host computer system, the host computer system comprising the processor, wherein the storage controller and the cache controller comprise one or more device drivers executing on the processor of the host computer system.

16. A computer program product comprising a non-transitory computer readable storage medium storing computer usable program code executable to perform operations for managing contents of a cache, the operations comprising:

monitoring read requests received for a non-volatile cache;

causing data of a read request to be read from a sequential log-based writing structure of the cache into volatile memory to service the read request;

determining whether the read request satisfies a frequent read threshold for the cache; and

causing data of the read request to be written forward to an append point of the sequential log-based writing structure of the cache without re-reading the data of the read request from a non-volatile storage medium of the cache in response to determining that the read request satisfies the frequent read threshold.

17. The computer program product of claim 16, wherein the operations further comprise identifying the data of the read request as frequently accessed data in response to determining that the read request satisfies the frequent read threshold.

18. An apparatus for managing contents of a cache, the apparatus comprising:

means for receiving a read request for data stored in a non-volatile cache;

means for reading the data from a storage region of a sequential log-based writing structure of the cache into volatile memory to service the read request; and

means for writing the data from the volatile memory forward to a different storage region of the sequential log-based writing structure of the cache without re-reading the data of the read request from a non-volatile storage medium of the cache in response to determining that the read request for the data satisfies a frequent read threshold for the cache.

19. The apparatus of claim 18, further comprising means for recovering storage capacity of the entire storage region subsequent to writing the data of the read request to the different storage region.