Management of external memory functioning as virtual cache

• US 8,631,203 B2
• Filed: 12/10/2007
• Issued: 01/14/2014
• Est. Priority Date: 12/10/2007
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Fortin, Michael, Ergan, Cenk, Iyigun, Mehmet, Bak, Yevgeniy, Mickle, Ben, Dietrich, Aaron, Kirshenbaum, Alexander
• Primary Examiner(s): KROFCHECK, MICHAEL C
• Application Number:
  US11/953,312
• Publication Number:
  US 20090150611A1
• Time in Patent Office: 2,227 Days
• Field of Search: None
• US Class Current: 711/118
• 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 computing device comprising:

a main system memory configured for storing a plurality of pages of data;

at least one auxiliary memory configured for storing the plurality of pages of data and for being removable from the computing device; and

a memory manager configured for controlling the caching of virtual pages of data on the at least one auxiliary memory, the memory manager further configured for identifying a virtual page of the virtual pages using a page key comprising a tuple, the page key configured for identifying the virtual page as cached in a file based on the tuple comprising the virtual page'"'"'s file identifier and its file offset information, and further configured for identifying the virtual page as employed by a process based on the tuple comprising the virtual page'"'"'s process identifier and its virtual address within the process, the memory manager further configured for verifying that virtual pages of data cached on the auxiliary memory are consistent with pages of data stored in the main system memory after the auxiliary memory is removed from the computing device and reconnected to the computing device, where the verifying is based on an analysis of non-time stamp virtual page data on the auxiliary memory.

2. The computing device computer system of claim 1, wherein the tuple of the page key comprises the virtual page'"'"'s originating file identifier and its originating file offset information corresponding to the virtual page being cached in the file, and wherein the tuple of the page key comprises the virtual page'"'"'s process identifier and its virtual address within the process corresponding to the virtual page being employed by the process.

3. The computing device of claim 1, 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.

4. The computing device of claim 3, wherein the at least one auxiliary memory includes a plurality of memories.

5. The computing device of claim 1, wherein virtual pages stored on the removable at least one auxiliary memory are encrypted.

6. The computing device of claim 1, wherein dirty virtual pages are stored on non-removable auxiliary memories, and clean virtual pages are stored on removable or non-removable auxiliary memories.

7. The computing device of claim 1, wherein the virtual pages are stored in compressed form on the at least one auxiliary memory.

8. The computing device of claim 1, wherein a virtual data authenticity indicator is used by the memory 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.

9. The computing device of claim 8, wherein the virtual data authenticity indicator includes a hash of the virtual page, and interruption of communication between the computing device and the auxiliary memory is caused by power down of the computing device or removal of the auxiliary memory from the computing device.

10. A method performed on a computing device for managing virtual pages cached in auxiliary memory, the method comprising:

providing a main system memory configured for storing a plurality of pages of data, and the auxiliary memory configured for storing the plurality of pages of data and for being removable from the computing device;

caching virtual pages of data on the auxiliary memory, a virtual page of the virtual pages being identified by a page key comprising a tuple, the page key configured for identifying the virtual page as cached in a file based on the tuple comprising the virtual page'"'"'s file identifier and its file offset information, and further configured for identifying the virtual page as employed by a process based on the tuple comprising virtual page'"'"'s process identifier and its virtual address within the process;

disconnecting the auxiliary memory from the computing device;

reconnecting the auxiliary memory to the computing device; and

verifying that virtual pages cached on the auxiliary memory are consistent with corresponding page data stored in the main system memory, the verifying performed after reconnecting the auxiliary memory to the computing device and based on an analysis of non-time stamp cached virtual page data on the auxiliary memory.

11. The method of claim 10, further comprising caching other virtual pages of data on the auxiliary memory, the virtual pages being identified by a page key that includes a tuple of process and virtual address information.

12. The method of claim 11, 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 computing device and the auxiliary memory is interrupted.

13. The method of claim 10, wherein the disconnecting and the reconnecting are performed without loss of data corresponding to the virtual pages stored on the at least one auxiliary memory.

14. The method of claim 10, wherein virtual pages stored on the auxiliary memory are encrypted.

15. The method of claim 10, 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.

16. The method of claim 10, wherein the virtual pages are stored in compressed form on the auxiliary memory.

17. The method of claim 10 further comprising:

first identifying, in response to the virtual page being cached in the file, the virtual page using the page key based on the tuple of the page key comprising the virtual page'"'"'s originating file identifier and its originating file offset information;

or

second identifying, in response to the virtual page being employed by the process, the virtual page using the page key based on the tuple of the page key comprising the virtual page'"'"'s process identifier and its virtual address within the process.

18. A method performed on a computing device for managing pages cached in memory, the method comprising:

providing a main system memory configured for storing a plurality of pages of data, and an auxiliary memory configured for storing the plurality of pages of data and for being removable from the computer system;

caching virtual pages of data on the auxiliary memory, a virtual page of the virtual pages being identified by a page key comprising a tuple, the page key configured for identifying the virtual page as cached in a file based on the tuple comprising the virtual page'"'"'s file identifier and file offset information, and further configured for identifying the virtual page as employed by a process based on the tuple comprising the virtual page'"'"'s process identifier and its virtual address within the process.

19. The method of claim 18 further comprising:

disconnecting the auxiliary memory from the computing device;

reconnecting the auxiliary memory to computing device to speed computing device operations; and

verifying that pages cached on the auxiliary memory are consistent with corresponding page data stored in another memory of the computer system, the verifying performed after reconnecting the auxiliary memory to the computer system and based on an analysis of non-time stamp cached page data on the auxiliary memory, wherein the 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 based on a list of changes maintained for the auxiliary memory.

20. The method of claim 18 further comprising:

first identifying, in response to the virtual page being cached in the file, the virtual page using the page key based on the tuple of the page key comprising the virtual page'"'"'s originating file identifier and its originating file offset information; and

second identifying, in response to the virtual page being employed by the process, the virtual page using the page key based on the tuple of the page key comprising the virtual page'"'"'s process identifier and its virtual address within the process.