Method, apparatus, and product for an efficient virtualized time base in a scaleable multi-processor computer

• US 20060242442A1
• Filed: 04/20/2005
• Published: 10/26/2006
• Est. Priority Date: 04/20/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Armstrong, William Joseph, Swaney, Scott Barnett, Nayar, Naresh, Corrigan, Michael J.
• Granted Patent: US 7,512,826 B2
• Time in Patent Office: Days
• US Class Current: 713/400
• CPC Class Codes: G06F 1/14 Time supervision arrangements, e.g. real time clock

Abstract

A method, apparatus, and computer program product are disclosed in a data processing system for providing a virtualized time base in a logically partitioned data processing system. A time base is determined for each one of multiple processor cores. The time base is used to indicate a current time to one of the processor cores for which the time base is determined. The time bases are synchronized together for the processor cores such that each one of the processor cores includes its own copy of a synchronized time base. For one of the processor cores, a virtualized time base is generated that is different from the synchronized time base but that remains synchronized with at least a portion of the synchronized time base. The processor core utilizes the virtualized time base instead of the synchronized time base for indicating the current time to the processor core. The synchronized time bases and the portion of the virtualized time base remaining in synchronization together.

Claims

1. A method for providing a virtualized time base in a logically partitioned data processing system, said method comprising:

determining a time base for each one of a plurality of processor cores, said time base being used to indicate a current time to one of said plurality of processor cores for which said time base is determined;

synchronizing said time bases together for said plurality of processor cores wherein each one of said plurality of processor cores includes its own copy of a synchronized time base;

generating, for one of said plurality of processor cores, a virtualized time base that is different from said synchronized time base but that remains synchronized with at least a portion of said synchronized time base;

utilizing, by said one of said plurality of processor cores, said virtualized time base instead of said synchronized time base for indicating said current time to said one of said plurality of processor cores; and

said synchronized time bases and said portion of said virtualized time base remaining in synchronization together.

2. The method according to claim 1, further comprising:

said synchronized time bases and said virtualized time base being represented using a plurality of bits that include first bits and second bits; and

generating said virtualized time base by modifying said first bits of said time base while said second bits of said time base remain unaffected, said virtualized time base including said modified first bits and said second bits.

3. The method according to claim 2, further comprising:

executing a move-to-special-purpose-register instruction that modifies only said first bits and leaves said second bits unaffected; and

said instruction writing a new value into only said first bits.

4. The method according to claim 2, further comprising:

said second bits of said time base continuing to remain synchronized to said second bits of said synchronized time base after said first bits are modified.

5. The method according to claim 4, further comprising:

executing one of a plurality of logical partitions on a first one of said plurality of processor cores in a first machine, said one of said plurality of processor cores utilizing said synchronized time base;

identifying a time base offset for said one of said plurality of logical partitions; and

modifying said first bits of said time base utilizing said time base offset.

6. The method according to claim 5, further comprising:

after modifying said first bits, determining whether said a time being represented by said second bits had carried over into said first bits while said first bits were being modified; and

in response to determining that said time being represented by said second bits had carried over into said first bits while said first bits were being modified, updating said first bits to represent said carry over.

7. The method according to claim 1, further comprising:

executing one of a first plurality of logical partitions on a first one of said plurality of processor cores in a first machine, said first one of said plurality of processor cores utilizing said synchronized time base;

suspending processing of said one of said plurality of logical partitions on said first machine;

transmitting said one of said plurality of logical partitions to a second machine for processing on one of a second plurality of processor cores that are included within said second machine;

determining a second time base for each one of said second plurality of processor cores;

synchronizing said second time bases together for said second plurality of processor cores wherein each one of said second plurality of processor cores includes its own copy of a second synchronized time base;

generating a second virtualized time base for said one of said second plurality of processor cores, said second virtualized time base being different from said second synchronized time base but remaining synchronized with at least a portion of said second synchronized time base; and

executing said one of said plurality of logical partitions utilizing said one of said second plurality of processor cores, said one of said second plurality of processor cores utilizing said second virtualized time base.

8. The method according to claim 7, further comprising:

creating said one of said first plurality of logical partitions on said first machine; and

generating, by said second machine, a time base offset for said one of said first plurality of logical partitions, said time base offset indicating a relative difference in time between said synchronized time base in said first machine and said second synchronized time base in said second machine.

9. The method according to claim 7, further comprising:

creating said one of said first plurality of logical partitions on said first machine;

prior to transmitting said one of said first plurality of logical partitions to said second machine, generating, by said first machine, a time base offset for said one of said first plurality of logical partitions, said time base offset being initially set equal to zero, said time base offset remaining static so long as said one of said first plurality of logical partitions is processed by said first machine and not transmitted to another machine;

modifying, by said second machine, said time base offset to indicate a relative difference in time between said synchronized time base in said first machine and said second synchronized time base in said second machine; and

said modified time base offset remaining static in said second machine so long as said one of said first plurality of logical partitions is processed by said second machine and is not transmitted to another machine.

10. The method according to claim 1, further comprising:

creating a logical partition by a first machine that includes said plurality of processor cores that utilize said synchronized time base;

transmitting said logical partition to a second machine for execution by said second machine, said second machine utilizing a second synchronized time base; and

determining a time base offset for said logical partition, said time base offset representing a difference between said first synchronized time base and said second synchronized time base.

11. The method according to claim 10, further comprising:

determining a second virtualized time base utilizing said time base offset; and

executing said logical partition by a processor core in said second machine, said processor core utilizing said second virtualized time instead of said second synchronized time base for indicating a current time to said processor core in said second machine.

12. The method according to claim 11, further comprising:

synchronizing said first machine to said second machine;

determining an elapsed time that occurred during said transmission logical partition from said first machine to said second machine; and

adjusting said second virtualized time base utilizing said elapsed time by adding said elapsed time to said time base offset.

13. The method according to claim 1, further comprising:

executing a first logical partition having a first time base offset utilizing a particular one of said plurality of processor cores;

suspending execution of said first logical partition;

identifying a second logical partition to be executed by said particular one of said plurality of processor cores;

identifying a second time base offset for said second logical partition;

determining a difference between said first time base offset and second time base offset;

determining a virtualized time base for said particular one of said plurality of processor cores by modifying first bits of said virtualized time base wherein said first bits represent said difference.

14. The method according to claim 1, further comprising:

identifying a next logical partition to be executed by a particular one of said plurality of processor cores;

identifying a first time base offset for said next logical partition;

determining a second time base offset for a previous logical partition that just finished being executed by said particular one of said plurality of processor cores;

determining a difference between said first time base offset and second time base offset;

determining a virtualized time base for said particular one of said plurality of processor cores by modifying first bits of said virtualized time base wherein said first bits represent said difference.

15. The method according to claim 14, further comprising:

executing a machine check in said particular one of said plurality of processor cores;

restoring a synchronized time base for said particular one of said plurality of processor cores from a time-of-day register that is maintained by a chip that includes said particular one of said plurality of processor cores;

said second time base offset being unknowable after said machine check occurs;

determining a difference between said first time base offset and time base that was restored from said time-of-day register;

determining a virtualized time base for said particular one of said plurality of processor cores by modifying first bits of said virtualized time base wherein said first bits represent said difference.

16. An apparatus for providing a virtualized time base in a logically partitioned data processing system, said apparatus comprising:

a time base determined for each one of a plurality of processor cores, said time base being used to indicate a current time to one of said plurality of processor cores for which said time base is determined;

said time bases being synchronized together for said plurality of processor cores wherein each one of said plurality of processor cores includes its own copy of a synchronized time base;

a virtualized time base, generated for one of said plurality of processor cores, that is different from said synchronized time base but that remains synchronized with at least a portion of said synchronized time base;

said one of said plurality of processor cores utilizing said virtualized time base instead of said synchronized time base for indicating said current time to said one of said plurality of processor cores; and

said synchronized time bases and said portion of said virtualized time base remaining in synchronization together.

17. The apparatus according to claim 16, further comprising:

a particular one of said plurality of processor cores, having a first time base offset, executing a first logical partition;

execution of said first logical partition being suspended;

a second logical partition to be executed by said particular one of said plurality of processor cores being identified;

a second time base offset for said second logical partition;

said system including a CPU executing code for determining a difference between said first time base offset and second time base offset; and

said code for determining a virtualized time base for said particular one of said plurality of processor cores by modifying first bits of said virtualized time base wherein said first bits represent said difference.

18. The apparatus according to claim 16, further comprising:

a particular one of said plurality of processor cores for executing a next logical partition;

a first time base offset for said next logical partition being identified;

said system including a CPU executing code for determining a second time base offset for a previous logical partition that just finished being executed by said particular one of said plurality of processor cores;

said code for determining a difference between said first time base offset and second time base offset; and

said code for determining a virtualized time base for said particular one of said plurality of processor cores by modifying first bits of said virtualized time base wherein said first bits represent said difference.

19. The apparatus according to claim 16, further

a first one of said plurality of processor cores in a first machine executing one of a first plurality of logical partitions, said first one of said plurality of processor cores utilizing said synchronized time base;

processing of said one of said plurality of logical partitions being suspended on said first machine;

said one of said plurality of logical partitions being transmitted to a second machine for processing on one of a second plurality of processor cores that are included within said second machine;

a second time base being determined for each one of said second plurality of processor cores;

said second time bases being synchronized together for said second plurality of processor cores wherein each one of said second plurality of processor cores includes its own copy of a second synchronized time base;

a second virtualized time base being generated for said one of said second plurality of processor cores, said second virtualized time base being different from said second synchronized time base but remaining synchronized with at least a portion of said second synchronized time base; and

said one of said second plurality of processor cores executing said one of said plurality of logical partitions, said one of said second plurality of processor cores utilizing said second virtualized time base.

20. A computer program product for providing a virtualized time base in a logically partitioned data processing system, said product comprising:

instructions for determining a time base for each one of a plurality of processor cores, said time base being used to indicate a current time to one of said plurality of processor cores for which said time base is determined;

instructions for synchronizing said time bases together for said plurality of processor cores wherein each one of said plurality of processor cores includes its own copy of a synchronized time base;

instructions for generating, for one of said plurality of processor cores, a virtualized time base that is different from said synchronized time base but that remains synchronized with at least a portion of said synchronized time base;

instructions for utilizing, by said one of said plurality of processor cores, said virtualized time base instead of said synchronized time base for indicating said current time to said one of said plurality of processor cores; and

said synchronized time bases and said portion of said virtualized time base remaining in synchronization together.