MANAGEMENT OF EXTERNAL MEMORY FUNCTIONING AS VIRTUAL CACHE

• US 20090150611A1
• Filed: 12/10/2007
• Published: 06/11/2009
• Est. Priority Date: 12/10/2007
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Fortin, Michel, Mickle, Ben, Bak, Yevgeniy, Ergan, Cenk, Kirshenbaum, Alexander, Iyigun, Mehmet, Dietrich, Aaron
• Granted Patent: US 8,631,203 B2
• Time in Patent Office: Days
• US Class Current: 711/115
• CPC Class Codes: G06F 12/0815 Cache consistency protocols
• CPC Class Codes: G06F 12/0893 Caches characterised by their organisation or structure
• CPC Class Codes: G06F 12/1009 using page tables, e.g. page table structures
• CPC Class Codes: G06F 12/1408 by using cryptography for digital transmission H04L9/00

Abstract

A method and apparatus for managing the caching of data on an auxiliary memory of a computer. Pages of data may be cached on an auxiliary memory, such as a flash memory, at a virtual level using an identifier that does not involve a physical address of the pages on a memory. Pages may be cached on auxiliary memory that may be removable from the computer, e.g., by unplugging the memory from the computer. Page data may be encrypted and/or compressed on the auxiliary memory. An authentication indicator may be used to verify the accuracy of cached data in the case of an interrupted connection to the auxiliary memory, e.g., as a result of computer power down, hibernation, removal of the memory from the computer, etc.

Claims

1. A computer system comprising:

a processor adapted to execute instructions to carry out one or more functions;

a main system memory adapted to store a plurality of pages of data that are used by the processor in performing the one or more functions;

at least one auxiliary memory in direct or indirect communication with the processor, the at least one auxiliary memory adapted to store a plurality of pages of data for use by the processor; and

a cache manager that controls the caching of virtual pages of data for use by the processor on the at least one auxiliary memory, the cache manager identifying virtual pages using a virtual identifier that is not an address that defines a physical location of the virtual page on a memory.

2. The computer system of claim 1, wherein the virtual identifier includes a page key that includes a block of memory defining the corresponding virtual page that includes a tuple of file and offset information, or a tuple of process and virtual address information.

3. The computer system of claim 1, wherein the at least one auxiliary memory device is removable from the computer system.

4. The computer system of claim 3, wherein the at least one auxiliary memory is removable from the computer system without loss of data corresponding to the virtual pages stored on the at least one auxiliary memory.

5. The computer system of claim 4, wherein the at least one auxiliary memory includes a plurality of memories.

6. The computer system of claim 3, wherein virtual pages stored on the removable at least one auxiliary memory are encrypted.

7. The computer system of claim 3, wherein dirty virtual pages are stored on non-removable auxiliary memories, and clean virtual pages are stored on removable and/or non-removable auxiliary memories.

8. The computer system of claim 1, wherein the virtual pages are stored in compressed form on the at least one auxiliary memory.

9. The computer system of claim 1, wherein a virtual data authenticity indicator is used by the cache manager to verify that a virtual page on an auxiliary memory remains unchanged after communication between the computer system and the auxiliary memory is interrupted.

10. The computer system of claim 9, wherein the virtual data authenticity indicator includes a hash of the virtual page, and interruption of communication between the computer system and the auxiliary memory is caused by power down of the computer or removal of the auxiliary memory from the computer system.

11. A method of managing virtual pages cached in auxiliary memory of a computer system, comprising:

providing a computer system including a processor adapted to execute instructions to carry out one or more functions, a main system memory adapted to store a plurality of pages of data that are used by the processor in performing the one or more functions, and an auxiliary memory in direct or indirect communication with the processor, the auxiliary memory adapted to store a plurality of pages of data for use by the processor;

caching virtual pages of data for use by the processor on the auxiliary memory; and

disconnecting the auxiliary memory from the computer system.

12. The method of claim 11, wherein the virtual pages are identified by a page key that is not an address that defines a physical location of the virtual page on a memory.

13. The method of claim 12, wherein the page key includes a tuple of file and offset information, or a tuple of process and virtual address information.

14. The method of claim 11, further comprising removing the auxiliary memory from the computer system without loss of data corresponding to the virtual pages stored on the at least one auxiliary memory.

15. The method of claim 11, wherein virtual pages stored on the auxiliary memory are encrypted.

16. The method of claim 11, wherein the step of caching virtual pages includes:

caching dirty virtual pages on non-removable auxiliary memory, and

caching clean virtual pages on removable auxiliary memory.

17. The method of claim 11, wherein the virtual pages are stored in compressed form on the auxiliary memory.

18. The method of claim 13, further comprising:

generating a virtual data authenticity indicator used to verify that a virtual page on an auxiliary memory remains unchanged after communication between the computer system and the auxiliary memory is interrupted.

19. A method of managing pages cached in memory of a computer system, comprising:

providing a computer system including a processor adapted to execute instructions to carry out one or more functions, main system memory adapted to store a plurality of pages of data that are used by the processor in performing the one or more functions, and an auxiliary memory in direct or indirect communication with the processor, the auxiliary memory adapted to store a plurality of pages of data for use by the processor and being removable from the computer system;

caching pages of data for use by the processor on the auxiliary memory;

disconnecting the auxiliary memory from the computer system;

reconnecting the auxiliary memory to the computer system to speed computer system operations; and

verifying that pages cached on the auxiliary memory are consistent with corresponding page data stored in another memory of the computer system.

20. The method of claim 19, wherein the step of verifying includes:

comparing data cached on the auxiliary memory with the corresponding data stored on the source memory of the computer system from which the data was cached, or

assessing whether an authenticity indicator for the data cached on the auxiliary memory indicates a change in the data;

or

determining whether changes to the data cached on the auxiliary memory have occurred by consulting a list of changes maintained for the auxiliary memory.