Systems and methods for caching with file-level granularity

• US 20020124135A1
• Filed: 03/01/2001
• Published: 09/05/2002
• Est. Priority Date: 03/01/2001
• Status: Active Grant

• Current Assignee: Stratus Technologies Ireland Ltd. (Stratus Technologies Bermuda Holdings Ltd.)
• Original Assignee: Stratus Technologies Bermuda Ltd. (Stratus Technologies Bermuda Holdings Ltd.)
• Inventors: Newman, Otto R.
• Granted Patent: US 6,766,413 B2
• Time in Patent Office: Days
• US Class Current: 711/113
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2212/463 File

Abstract

Systems and methods for implementing improved disk caching in a programmed computer. Improved disk caching is achieved through apparatus and methods that permit the designation of files or types of files as memory-resident, transient, or normal (i.e., neither memory-resident or transient). The disk blocks associated with a memory-resident file are loaded immediately into cache memory in whole or in part, or are loaded on a block-by-block basis as they are accessed. The blocks of a memory-resident file remain in cache until the file is designated not memory resident, whereupon the blocks become purgeable, or until cache size limits force the removal of blocks from the cache. The blocks are purged immediately in whole or in part, or displaced gradually as blocks from other memory-resident files displace them. The blocks of a transient file are maintained in cache for a shorter duration before removal, freeing resources to cache other blocks.

Claims

1. A method for improved access to data files comprising the steps:

(a) designating a portion of volatile memory to be used as a cache memory;

(b) receiving a designation of a file as memory resident; and

(c) maintaining at least one of a data block and an index block corresponding to said designated file in said cache memory for an extended duration.

2. The method of claim 1 wherein step (b) occurs while an application is accessing said data file.

3. The method of claim 1 wherein step (b) comprises a user designating a file as memory-resident.

4. The method of claim 1 wherein step (b) comprises a computer program designating a file as memory-resident.

5. The method of claim 1 wherein step (c) comprises the steps:

(c-a) accessing at least one of a disk block and an index block associated with a designated file in a non-volatile memory; and

(c-b) storing the contents of said accessed block in said cache memory.

6. The method of claim 1 wherein said volatile memory is random-access memory (RAM).

7. The method of claim 1 wherein said cache memory is a sub-cache memory contained within a cache memory.

8. The method of claim 1 further comprising the step of (d) modifying the size of the cache memory.

9. The method of claim 8 wherein step (d) is performed by the user.

10. The method of claim 8 wherein step (d) is performed without user interaction.

11. The method of claim 1 further comprising the steps of:

(d) receiving an indicator corresponding to a maximum size of said cache memory; and

(e) limiting the size of said cache memory to said maximum size indicated by removing a maintained data block from said cache memory.

12. The method of claim 1 further comprising the steps of:

(d) receiving a designation of a data file as not memory-resident; and

(e) processing at least one of a data block and an index block corresponding to said designated file using default caching methods.

14. The method of claim 13 wherein step (c) comprises the steps:

(c-a) delaying writing said at least one of a data block and an index block corresponding to said designated file to a non-volatile memory until the passage of said nominal duration; and

(c-b) removing said at least one of a data block and an index block corresponding to said designated file from said cache memory after the completion of step (c-a).

15. The method of claim 13 wherein step (b) occurs while an application is accessing said data file.

16. The method of claim 13 wherein step (b) is performed by a user.

17. The method of claim 13 wherein step (b) is performed without user interaction.

18. The method of claim 13 wherein said volatile memory is random-access memory (RAM).

19. The method of claim 13 further comprising the steps of:

(d) receiving a designation of a data file as not transient; and

(e) processing at least one of a data block and an index block corresponding to said designated file using default caching methods.

13. A method for improved access to data files comprising the steps:

(a) designating a portion of volatile memory to be used as a cache memory;

(b) receiving a designation of a file as transient; and

(c) maintaining at least one of a data block and an index block corresponding to said designated file in said cache memory for a nominal duration.

20. A programmed computer with an improved cache system, comprising:

a non-volatile memory comprising a file, said file comprising;

a disk block; and

an attribute field having a value equal to at least one of transient and memory-resident; and

a volatile memory comprising;

a cache comprising a data block, said data block corresponding to a file whose attribute field has a value equal to memory-resident; and

a queue comprising a data structure, said data structure corresponding to a data block stored in said cache,

wherein said data structure may only be removed from said queue in satisfaction of size constraints on said cache.

21. The computer of claim 20 wherein said size constraints on said cache may be modified.

22. The computer of claim 20 wherein said disk block is at least one of an index block and a data block.

23. The computer of claim 20 wherein said queue comprises:

a first queue comprising a data structure, said data structure corresponding to a disk block, said disk block corresponding to a file whose attribute field has a value equal to memory-resident; and

a second queue comprising a data structure, said data structure corresponding to a disk block, said disk block corresponding to a file whose attribute field has a value equal to transient.