MULTIPLE TIME GRANULARITY SUPPORT FOR ONLINE CLASSIFICATION OF MEMORY PAGES BASED ON ACTIVITY LEVEL

• US 20120011508A1
• Filed: 07/08/2011
• Published: 01/12/2012
• Est. Priority Date: 07/12/2010
• Status: Active Grant

• Current Assignee: Vmware LLC (Broadcom, Inc.)
• Original Assignee: VMware, Inc. (Broadcom, Inc.)
• Inventors: AHMAD, Irfan
• Granted Patent: US 8,990,531 B2
• Time in Patent Office: Days
• US Class Current: 718/1
• CPC Class Codes: G06F 12/1009 using page tables, e.g. page table structures
• CPC Class Codes: G06F 2009/45583 Memory management, e.g. access or allocation
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects

Abstract

Activity level of memory pages is classified in virtual machine environment, so that processes such as live VM migration and checkpointing, among others, can be carried out more efficiently. Because each such hypervisor-based service may desire classification of activity levels of memory pages at different frequencies and different time granularities, the hypervisor supports methods to classify activity levels of memory pages for a plurality of time intervals.

Claims

1. A method for classifying activity levels for memory pages of a virtual machine, the method comprising:

receiving notification of an elapse of one of a plurality of supported time intervals;

identifying a current activity level for a memory page of the virtual machine stored in a data structure maintained for the elapsed time interval;

retrieving input data indicating an activity level of the memory page during the elapsed time interval;

determining a new activity level for the memory page based on the current activity level and the retrieved input data; and

storing the new activity level in an entry of the data structure corresponding to the memory page.

2. The method of claim 1, wherein said determining comprises:

transitioning from the current activity level to the new activity level in a finite state machine based on the retrieved input data.

3. The method of claim 2, wherein the elapsed time interval is a minimum time interval supported by a hypervisor of the virtual machine and the retrieved input data is based on A/D bits of a page table entry for the memory page.

4. The method of claim 2, wherein the elapsed time interval is greater than a minimum time interval supported by a hypervisor of the virtual machine and the input data is based on at least a second current activity level for the memory page stored in a second data structure for a second time interval from the plurality of supported time intervals.

5. The method of claim 4, wherein the second time interval is the minimum time interval.

6. The method of claim 4, wherein the finite state machine differs from a second finite state machine used to determine activity levels for the second time interval.

7. The method of claim 2, wherein the elapsed time interval is greater than a minimum time interval supported by a hypervisor of the virtual machine and the retrieved input data is based on a summary bit set by the hypervisor if A/D bits of a page table entry for the memory page were set during the elapsed time interval but were subsequently cleared by the hypervisor while determining an activity level for a minimum time interval occurring within the elapsed time interval.

8. The method of claim 1, wherein the elapsed time interval is greater than a minimum time interval supported by a hypervisor of the virtual machine and the retrieved input data is a history of activity levels for the memory page recorded for the minimum time intervals during the elapsed time interval.

9. A computer system including one or more virtual machines running therein and a hypervisor configured to classify activity levels for memory pages of a virtual machine for a plurality of supported time intervals by performing the steps of:

receiving notification of an elapse of one of the plurality of supported time intervals;

identifying a current activity level for a memory page of the virtual machine stored in a data structure maintained for the elapsed time interval;

retrieving input data indicating an activity level of the memory page during the elapsed time interval;

determining a new activity level for the memory page based on the retrieved input data;

storing the new activity level in an entry of the data structure corresponding to the memory page.

10. The computer system of claim 9, wherein the determining step comprises transitioning from the current activity level to the new activity level in a finite state machine based on the retrieved input data.

11. The computer system of claim 10, wherein the elapsed time interval is a minimum time interval supported by a hypervisor of the virtual machine and the retrieved input data is based on A/D bits of a page table entry for the memory page.

12. The computer system of claim 10, wherein the elapsed time interval is greater than a minimum time interval supported by a hypervisor of the virtual machine and the input data is based on at least a second current activity level for the memory page stored in a second data structure for a second time interval from the plurality of supported time intervals.

13. The computer system of claim 12, wherein the second time interval is the minimum time interval.

14. The computer system of claim 12, wherein the finite state machine differs from a second finite state machine used to determine activity levels for the second time interval.

15. The computer system of claim 10, wherein the elapsed time interval is greater than a minimum time interval supported by a hypervisor of the virtual machine and the retrieved input data is based on a summary bit set by the hypervisor if A/D bits of a page table entry for the memory page were set during the elapsed time interval but were subsequently cleared by the hypervisor while determining an activity level for a minimum time interval occurring within the elapsed time interval.

16. The computer system of claim 9, wherein the elapsed time interval is greater than a minimum time interval supported by a hypervisor of the virtual machine and the retrieved input data is a history of activity levels for the memory page recorded for the minimum time interval during the elapsed time interval.

17. A computer-readable storage medium including instructions that, when executed by a computer processor, causes the computer processor to classify activity levels for memory pages of a virtual machine by performing the steps of:

receiving notification of an elapse of one of a plurality of supported time intervals;

identifying a current activity level for a memory page of the virtual machine stored in a data structure maintained for the elapsed time interval;

retrieving input data indicating an activity level of the memory page during the elapsed time interval;

determining a new activity level for the memory page based on the retrieved input data;

storing the new activity level in an entry of the data structure corresponding to the memory page.

18. The computer-readable storage medium of claim 17, wherein the determining step comprises transitioning from the current activity level to the new activity level in a finite state machine based on the retrieved input data.

19. The computer-readable storage medium of claim 18, wherein the elapsed time interval is a minimum time interval supported by a hypervisor of the virtual machine and the retrieved input data is based on A/D bits of a page table entry for the memory page.

20. The computer-readable storage medium of claim 18, wherein the elapsed time interval is greater than a minimum time interval supported by a hypervisor of the virtual machine and the input data is based on at least a second current activity level for the memory page stored in a second data structure for a second time interval from the plurality of supported time intervals.

21. The computer-readable storage medium of claim 20, wherein the second time interval is the minimum time interval.

22. The computer-readable storage medium of claim 20, wherein the finite state machine differs from a second finite state machine used to determine activity levels for the second time interval.

23. The computer-readable storage medium of claim 18, wherein the elapsed time interval is greater than a minimum time interval supported by a hypervisor of the virtual machine and the retrieved input data is based on a summary bit set by the hypervisor if A/D bits of a page table entry for the memory page were set during the elapsed time interval but were subsequently cleared by the hypervisor while determining an activity level for a minimum time interval occurring within the elapsed time interval.

24. The computer-readable storage medium of claim 17, wherein the elapsed time interval is greater than a minimum time interval supported by a hypervisor of the virtual machine and the retrieved input data is a history of activity levels for the memory page recorded for the minimum time interval during the elapsed time interval.