Adaptive reader-writer lock

• US 6,678,772 B2
• Filed: 12/19/2000
• Issued: 01/13/2004
• Est. Priority Date: 12/19/2000
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: McKenney, Paul E.
• Primary Examiner(s): Auve, Glenn A.
• Assistant Examiner(s): VU, TRISHA U
• Application Number:
  US09/741,679
• Publication Number:
  US 20020078284A1
• Time in Patent Office: 1,120 Days
• Field of Search: 710/108, 710/200, 709/104, 709/107, 703/21, 703/22
• 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 a measure of read-side acquisitions by a unit within a computer processing system;

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

(c) 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, wherein said unit is selected from the group consisting of:

a CPU, a thread, a processor, a transaction, a co-routine, a thread in a multi-threaded architecture, and a task.

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

6. 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.

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

8. The method of claim 1, further comprising combining the measure of read-side acquisitions by the unit with data stored in the system-wide measure whenever the unit acquires a write lock.

9. The method of claim 8, further comprising resetting the measure of read-side acquisitions by the unit to zero.

10. 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.

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

12. The method of claim 11, wherein maintaining the system-wide measure of read-hold duration includes maintaining a measure of read-hold duration by the unit.

13. The method of claim 11, 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.

14. The method of claim 11, 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.

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

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

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

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

18. A computer system, comprising:

multiple processors;

a counter for measuring read-side acquisitions by a unit within a computer processing system;

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

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

19. The system of claim 18, 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.

20. The system of claim 19, 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.

21. The system of claim 18, wherein said unit is selected from the group consisting of:

a CPU, a thread, a process, a transaction, a co-routine, a thread in a multi-threaded architecture, and task.

22. The system of claim 18, 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.

23. The system of claim 18, 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.

24. The system of claim 18, 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.

25. The system of claim 18, 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.

26. An article comprising:

a computer-readable signal bearing medium;

means in the medium for maintaining a measure of read-side acquisitions by a unit within a computer processing system having multiple processors;

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

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

27. The article of claim 26, wherein the medium is selected from the group consisting of:

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

28. The article of claim 26, 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.

29. The article of claim 26, wherein the unit is selected from the group consisting of:

a CPU, a thread, a process, a transaction, a co-routine, a thread in a multi-threaded architecture, and a task.

30. The article of claim 26, 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.

31. The article of claim 26, 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.

32. The article of claim 26, wherein the lock mode is a centralized lock mode, and wherein said lock mode manager is responsive to a system-wide measure of read acquisitions and a system-wide measure of read-hold duration.

33. The article of claim 26, 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.

34. The article of claim 26, wherein at least some of said second system-wide measures are selected from the group consisting of:

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