Adaptive reader-writer lock

• US 7,191,272 B2
• Filed: 12/09/2003
• Issued: 03/13/2007
• 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): Perveen; Rehana
• Assistant Examiner(s): VU, TRISHA U
• Application Number:
  US10/731,454
• Publication Number:
  US 20040117531A1
• Time in Patent Office: 1,190 Days
• Field of Search: 710/200, 710/108, 709/104, 709/107, 709/214, 711/147, 711/150, 711/151, 711/152, 707/8, 718/100, 718/104, 718/105, 718/106
• 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 in a multiprocessor, comprising:

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

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

(c) acquiring said lock for a first processing unit responsive to said determination; and

(d) releasing said lock responsive to a change in at least some of said system-wide measures of read and write acquisitions, wherein the step of releasing said lock includes switching said first processing unit to a different lock.

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

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

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

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

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

5. The method of claim 4, wherein said determining step is further responsive to a quantity of units in the system.

6. The method of claim 5, 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 multi-threaded architecture, a NUMA module, and a task.

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

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

9. The method of claim 8, wherein the step of maintaining a system-wide measure of read-hold duration includes maintaining a measure of read-hold duration by a unit.

10. The method of claim 9, 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 multi-threaded architecture, a NUMA module, and a task.

11. The method of claim 8, wherein the lock is a centralized lock, and wherein said determining step is responsive to the system-wide measures of read acquisitions and read-hold duration.

12. The method of claim 8, wherein the lock is an exclusive lock and wherein said determining step is responsive to the system-wide measure of read-hold duration.

13. The method of claim 12, wherein said determining step is further responsive to the system-wide measure of read acquisitions.

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

15. 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.

16. A computer system comprising:

multiple processors;

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

a lock manager adapted to select a lock for acquisition by a first processing unit responsive to at least some of said measure and to release said acquired lock responsive to a change in at least some of said measures, wherein said manager release of said lock includes a switch of said first processing unit to a different lock.

17. The system of claim 16, wherein said lock is selected from a group consisting of:

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

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

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

19. The system of claim 16, wherein the lock is a distributed reader-writer lock, and wherein said lock manager is responsive to the system-wide measure of write acquisitions and the system wide measure of read acquisitions.

20. The system of claim 16, wherein the lock is a centralized lock, and wherein said lock manager is responsive to the system-wide measure of write acquisitions and the system-wide measure of read acquisitions.

21. The system of claim 16, wherein the lock is a centralized lock, and wherein said lock manager is responsive to the system-wide measure of read acquisitions and a system-wide measure of read-hold duration.

22. The system of claim 16, wherein the lock is an exclusive lock and wherein said lock manager is responsive to a system-wide measure of read-hold duration.

23. 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 for a first processing unit responsive to at least some of said measures, and for releasing said lock responsive to a change in at least some of said system-wide measures of read and write acquisitions, wherein said means for releasing said lock includes switching said first processing unit to a different lock.

24. The article of claim 23, wherein the medium is selected from a group consisting of:

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

25. The article of claim 23, wherein said lock is selected from a group consisting of:

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

26. The article of claim 23, wherein the lock is a distributed reader-writer lock, and wherein said means in the medium for selecting a lock is responsive to the system-wide measure of writer acquisitions and the system wide measure of read-acquisitions.

27. The article of claim 23, wherein the lock is a centralized lock, and wherein said means in the medium for selecting a lock is response to the system-wide measure of write acquisitions and the system-wide measure of read acquisitions.

28. The article of claim 23, wherein the lock is a centralized lock, and wherein said means in the medium for selecting a lock is responsive to a system-wide measure of read acquisitions and a system-wide measure of read-hold duration.

29. The article of claim 23, wherein the lock is an exclusive lock and wherein said means in the medium for selecting a lock is responsive to a system-wide measure of read-hold duration.

30. The article of claim 23, wherein at least some of said second system-wide measures are selected from a group consisting of:

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