Adaptive reader-writer lock

• US 20040117531A1
• Filed: 12/09/2003
• Published: 06/17/2004
• Est. Priority Date: 12/19/2000
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: McKenney, Paul E.
• Granted Patent: US 7,191,272 B2
• Time in Patent Office: Days
• US Class Current: 710/200
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

A method and computer system for dynamically selecting an optimal lock mode in a multiprocessor environment. The method determines a quantity of read-side and write-side acquisitions, and evaluates the data to determine an optimal lock mode for efficiently operating the computer system while maintaining reduced overhead. The method incorporates data received from the individual units within a central processing system, the quantity of write-side acquisitions in the system, and data which has been subject to secondary measures, such as formatives of digital filters. The data subject to secondary measures includes, but is not limited to, a quantity of read-side acquisitions, a quantity of write-side acquisitions, and a quantity of read-hold durations. Based upon the individual unit data and the system-wide data, including the secondary measures, the operating system may select the most efficient mode of operation from among the locking modes available. Accordingly, efficiency of a computer system may be enhanced with the ability to selectively choose an optimal locking mode based upon selected and calculated parameters.

Claims

1. A method for dynamically determining a lock mode in a multiprocessor, comprising:

(a) maintaining first and second system-wide measures of read and write acquisitions; and

(b) determining a lock mode based upon at least some of said measures.

2. The method of claim 1, wherein said lock mode is selected from the group consisting of:

a distributed reader-writer lock mode, a centralized reader-writer lock mode, and an exclusive lock mode.

3. The method of claim 2, wherein said exclusive lock mode is selected from the group consisting of:

a test and set lock mode, a test and test and set lock mode, a queued lock mode, a ticket lock mode, and a quad-aware lock mode.

4. The method of claim 1, further comprising switching to the lock mode from another lock mode.

5. The method of claim 1, wherein the lock mode is a distributed reader-writer lock mode, and wherein said determining step is responsive to the system-wide measure of write acquisitions and the system-wide measure of read acquisitions.

6. The method of claim 5, wherein said determining step is further responsive to a quantity of units in the system.

7. The method of claim 6, wherein said unit is selected from a group consisting of:

a CPU, a thread, a processor, a transaction, a co-routine, a thread in a multithreaded architecture, a NUMA module, and a task.

8. The method of claim 1, wherein the lock mode is a centralized lock mode, and wherein said determining step is responsive to the system-wide measure of write acquisitions and the system-wide measure of read acquisitions.

9. The method of claim 1, further comprising maintaining a system-wide measure of read-hold duration.

10. The method of claim 9, wherein the step of maintaining a system-wide measure of read-hold duration includes maintaining a measure of read-hold duration by a unit.

11. The method of claim 10, wherein said unit is selected from a group consisting of:

a CPU, a thread, a processor, a transaction, a co-routine, a thread in a multithreaded architecture, a NUMA module, and a task.

12. The method of claim 9, wherein the lock mode is a centralized lock mode, and wherein said determining step is responsive to the system-wide measures of read acquisitions and read-hold duration.

13. The method of claim 9, wherein the lock mode is an exclusive lock mode and wherein said determining step is responsive to the system-wide measure of read-hold duration.

14. The method of claim 13, wherein said determining step is further responsive to the system-wide measure of read acquisitions.

15. The method of claim 1, further comprising periodically updating at least some of said system-wide measures.

16. The method of claim 1, wherein at least some of said second system-wide measures are selected from a group consisting of:

a digital filter, a weighted average, a sliding window average, a finite impulse response, and a central data structure.

17. A computer system comprising:

multiple processors;

first and second system-wide measures of read and write acquisitions of said processors; and

a lock mode manager adapted to select a lock mode responsive to at least some of said measures.

18. The system of claim 17, wherein said lock mode is selected from a group consisting of:

a distributed reader-writer lock mode, a centralized reader-writer lock mode, and an exclusive lock mode.

19. The system of claim 18, wherein said exclusive lock mode is selected from a group consisting of:

a test and set lock mode, a test and test and set lock mode, a queued lock mode, a ticket lock mode, and a quad-aware lock mode.

20. The system of claim 17, wherein the lock mode is a distributed reader-writer lock mode, and wherein said lock mode manager is responsive to the system-wide measure of write acquisitions and the system wide measure of read acquisitions.

21. The system of claim 17, wherein the lock mode is a centralized lock mode, and wherein said lock mode manager is responsive to the system-wide measure of write acquisitions and the system-wide measure of read acquisitions.

22. The system of claim 17, wherein the lock mode is a centralized lock mode, and wherein said lock mode manager is responsive to the system-wide measure of read acquisitions and a system-wide measure of read-hold duration.

23. The system of claim 17, wherein the lock mode is an exclusive lock mode and wherein said lock mode manager is responsive to a system-wide measure of read-hold duration.

24. In a multiprocessor system, an article comprising:

a computer-readable signal bearing medium;

means in the medium for maintaining first and second system-wide measures of read and write acquisitions; and

means in the medium for selecting a lock mode responsive to at least some of said measures.

25. The article of claim 24, wherein the medium is selected from a group consisting of:

a recordable data storage medium, and a modulated carrier signal.

26. The article of claim 24, wherein said lock mode is selected from a group consisting of:

a distributed reader-writer lock mode, a centralized reader-writer lock mode, and an exclusive lock mode.

27. The article of claim 24, wherein the lock mode is a distributed reader-writer lock mode, and wherein said means in the medium for selecting a lock mode is responsive to the system-wide measure of writer acquisitions and the system wide measure of read-acquisitions.

28. The article of claim 24, wherein the lock mode is a centralized lock mode, and wherein said means in the medium for selecting a lock mode is response to the system-wide measure of write acquisitions and the system-wide measure of read acquisitions.

29. The article of claim 24, wherein the lock mode is a centralized lock mode, and wherein said means in the medium for selecting a lock mode is responsive to a system-wide measure of read acquisitions and a system-wide measure of read-hold duration.

30. The article of claim 24, wherein the lock mode is an exclusive lock mode and wherein said lock mode manager is responsive to a system-wide measure of read-hold duration.

31. The article of claim 24, wherein at least some of said second system-wide measures are selected from a group consisting of:

a digital filter, a weighted average, a sliding window average, a finite impulse response, and a central data structure.