Paravirtualized migration counter

Patent metadata

Field	Value
Publication number	US-9378057-B2
Application number	US-201414193344-A
Country	US
Kind code	B2
Filing date	Feb 28, 2014
Priority date	Feb 28, 2014
Publication date	Jun 28, 2016
Grant date	Jun 28, 2016

Abstract

An application associated with a processor reads a first value of a counter and a second value of the counter. The counter is indicative of a migration status of the application with respect to the processor. Responsive to determining that the first value of the counter does not equal the second value of the counter, the application ascertains whether a value of a hardware parameter associated with the processor has changed during a time interval. The migration status indicates a count of the number of times the application has migrated from one processor to another processor. The application determines the validity of a value of a performance monitoring unit derived from the hardware parameter in view of the application ascertaining whether the value of the hardware parameter has changed during the time interval.

First claim

What is claimed is:

1. A method, comprising:
determining, by a processing device, a first value of a counter and a second value of the counter, wherein the counter is indicative of a migration status of an application with respect to the processing device;
responsive to determining that the first value of the counter does not equal the second value of the counter, ascertaining whether a value of a hardware parameter associated with the processing device has changed during a time interval; and
determining, by the processing device, validity of a value of a performance monitoring unit derived from the hardware parameter in view of said ascertaining.

2. The method of claim 1 , wherein the migration status indicates a count of the number of times the application has migrated to another processing device.

3. The method of claim 1 , wherein determining the validity of the value of the performance monitoring unit further comprises determining that the value of the performance monitoring unit is invalid responsive to determining that the second value of the counter differs from the first value of the counter by more than one count.

4. The method of claim 1 , wherein determining the validity of the value of the performance monitoring unit further comprises reading a third value of the counter responsive to determining that the value of the hardware parameter has changed by one count during the time interval.

5. The method of claim 4 , wherein determining the validity of the value of the performance monitoring unit further comprises determining that the value of the performance monitoring unit is valid responsive to determining that the third value of the counter differs from the first value of the counter by one count and the value of hardware parameter has not changed during the time interval.

6. The method of claim 4 , wherein determining the validity of the value of the performance monitoring unit further comprises determining that the value of the performance monitoring unit is invalid responsive to determining that the third value of the counter differs from the first value of the counter by one count and the value of hardware parameter has changed during the time interval.

7. The method of claim 1 , wherein the hardware parameter is provided by at least one of an operating frequency of the processing device or a cache-line size of the processing device.

8. The method of claim 1 , wherein the performance monitoring unit is provided by at least one of a time stamp count or a count of cache misses.

9. The method of claim 1 , further comprising retrieving the first value of the counter from a model-specific register.

10. The method of claim 1 , further comprising retrieving the first value of the counter from a memory space of the application.

11. The method of claim 1 , wherein determining the first value of the counter comprises performing a system call to a hypervisor.

12. The method of claim 1 , wherein the application is provided by a virtual machine.

13. A system, comprising:
a memory;
a processing device, operatively coupled to the memory, the processing device to:
determine a first value of a counter and a second value of the counter, wherein the counter is indicative of a migration status of an application with respect to the processing device;
responsive to determining that the first value of the counter does not equal the second value of the counter, ascertain whether a value of a hardware parameter associated with the processing device has changed during a time interval; and
determine validity of a value of a performance monitoring unit derived from the hardware parameter in view of said ascertaining.

14. The system of claim 13 , wherein the migration status indicates a count of the number of times the application has migrated from one processor to another processing device.

15. The system of claim 13 , wherein the processing device is further to determine that the value of the performance monitoring unit is invalid responsive to determining that the second value of the counter differs from the first value of the counter by more than one count.

16. The system of claim 13 , wherein the processing device is further to read a third value of the counter responsive to determining that the value of the hardware parameter has changed by one count during the time interval.

17. A non-transitory computer-readable storage medium including instructions that, when accessed by a processing device, cause the processing device to:
determining, by the processing device, a first value of a counter and a second value of the counter, wherein the counter is indicative of a migration status of an application with respect to the processing device; and
responsive to determining that the first value of the counter does not equal the second value of the counter, ascertain whether a value of a hardware parameter associated with the processing device has changed during a time interval; and
determining, by the processing device, validity of a value of a performance monitoring unit derived from the hardware parameter in view of said ascertaining.

18. The non-transitory computer-readable storage medium of claim 17 , wherein the migration status indicates a count of the number of times the application has migrated from one processor to another processing device.

19. The non-transitory computer-readable storage medium of claim 17 , further comprising executable instructions causing the processing device to determine that the value of the performance monitoring unit to be invalid responsive to determining that the second value of the counter differs from the first value of the counter by more than one count.

20. The non-transitory computer-readable storage medium of claim 17 , further comprising executable instructions causing the processing device to read a third value of the counter responsive to determining that the value of the hardware parameter has changed by one count during the time interval.

Assignees

• Red Hat Israel Ltd

Inventors

• Noel Karen
• Bonzini Paolo
• Hod Ronen
• Tosatti Marcelo

Classifications

• G06F9/4555 Primary

  Para-virtualisation, i.e. guest operating system has to be modified · CPC title

• G06F11/3466

  Performance evaluation by tracing or monitoring · CPC title

• G06F11/3495

  for systems · CPC title

• G06F2009/4557

  Distribution of virtual machine instances; Migration and load balancing · CPC title

• G06F9/5088

  involving task migration · CPC title