Method and system for reducing context switch times

• US 7,603,673 B2
• Filed: 10/28/2004
• Issued: 10/13/2009
• Est. Priority Date: 10/28/2004
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: MacPherson, Mike
• Primary Examiner(s): An; Meng-Ai
• Assistant Examiner(s): To; Jennifer N
• Application Number:
  US10/975,571
• Publication Number:
  US 20060100986A1
• Time in Patent Office: 1,811 Days
• Field of Search: 718100-108, 712220-228, 710/48, 710/58, 710/59, 710/260
• US Class Current: 718/108
• CPC Class Codes: G06F 9/461 Saving or restoring of program or task context

Abstract

An apparatus for managing resource in a multithreaded system, and attempting to increase the speed in which task switching occurs by controlling when thread state is stored to memory. The apparatus includes a thread dispatcher circuit capable of determining, based upon an estimated state retirement rate associated with the worker threads and a rate of saving state of the worker threads, if the worker threads should be halted and saved the state of the worker threads.

Claims

1. A method comprising:

detecting a context switch request;

in response to detecting the context switch request, performing the operations;

halting a master thread from creating new worker threads,

estimating a retirement rate of a state associated with a plurality of worker threads; and

determining, based upon the estimated state retirement rate associated with the worker threads and a rate of saving state of the worker threads, if the worker threads should be halted and the state of the worker threads saved to a memory;

wherein in response to the determining, halting and saving the state of the worker threads to the memory if the rate of saving is greater than the estimated state retirement rate, and wherein the rate of saving is determined based on a portion of a bandwidth available to write to the memory.

2. The method of claim 1 further comprising,

if the rate of savings is not greater than the retirement rate, allowing the worker threads to naturally retire;

and

determining, based at least in part upon the state retirement rate of the worker threads, if the worker threads should be halted and the worker threads'"'"' state saved to memory.

3. The method of claim 1 wherein, estimating the retirement rate of the state associated with the worker threads comprises:

monitoring the thread retirement rate of the worker threads; and

estimating the state retirement rate based at least in part upon the thread retirement rate.

4. The method of claim 3, wherein estimating the state retirement rate based at least in part upon the thread retirement rate includes accounting for worker threads having variable size thread states.

5. The method of claim 3 wherein, monitoring the thread retirement rate of the worker threads comprises utilizing structures primarily capable of thread scheduling.

6. The method of claim 1, further comprising:

based at least in part upon the estimation of state retirement rate, prioritizing the order in which worker threads will be halted and the worker threads'"'"' state saved.

7. The method of claim 6 further comprising:

if the rate of savings is greater than the state retirement rate, halting and saving the state of the worker threads to a memory.

8. The method of claim 7 further comprising:

if the rate of savings is not greater than the state retirement rate,

allowing the worker threads to naturally retire, estimating the retirement rate of a state associated with worker threads,

based at least in part upon the estimation of state retirement rate, prioritizing the order in which worker threads will be halted and the worker threads'"'"' state saved, and

determining, based at least in part upon the state retirement rate of the worker threads, if the worker threads should be halted and the worker threads'"'"' state saved to memory.

9. An article comprising a machine storage medium having a plurality of machine accessible instructions, wherein when the instructions are executed, the instructions provide for:

detecting a context switch request; and

in response to detecting the context switch request, performing the steps of;

halting a master thread from creating new worker threads,

estimating a retirement rate of a state associated with a plurality of worker threads, and

determining, based upon the estimated state retirement rate associated with the worker threads and a rate of saving state of the worker threads, if the worker threads should be halted and the state of the worker threads saved to a memory,

wherein in response to the determining, halting and saving the state of the worker threads to the memory if the rate of saving is greater than the estimated state retirement rate, and wherein the rate of saving is determined based on a portion of a bandwidth available to write to the memory.

10. The article of claim 9 further comprising instructions providing for:

if the rate of savings is not greater than the retirement rate,

allowing the worker threads to naturally retire, and

determining, based at least in part upon the state retirement rate of the worker threads, if the worker threads should be halted and the worker threads'"'"' state saved to memory.

11. The article of claim 9 wherein, the instructions providing for estimating the retirement rate of a state associated with worker threads comprise instructions providing for:

monitoring the thread retirement rate of the worker threads; and

estimating the state retirement rate based at least in part upon the thread retirement rate.

12. The article of claim 11, wherein the instructions providing for estimating the state retirement rate based at least in part upon the thread retirement rate includes instructions providing for accounting for worker threads having variable size thread states.

13. The article of claim 11 wherein, the instructions providing for monitoring the thread retirement rate of the worker threads comprises instructions providing for utilizing structures primarily capable of thread scheduling.

14. The article of claim 9, further comprising instructions providing for:

based at least in part upon the estimation of state retirement rate, prioritizing the order in which worker threads will be halted and the worker threads'"'"' state saved.

15. The article of claim 14 further comprising instructions providing for:

if the rate of savings is greater than the state retirement rate, halting and saving the state of the worker threads to a memory.

16. The article of claim 15 further comprising instructions providing for:

if the rate of savings is not greater than the state retirement rate,

allowing the worker threads to naturally retire,

based at least in part upon the estimation of state retirement rate, prioritizing the order in which worker threads will be halted and the worker threads'"'"' state saved and

determining, based at least in part upon the state retirement rate of the worker threads, if the worker threads should be halted and the worker threads'"'"' state saved to memory.

17. An apparatus comprising:

a processor executing a plurality of worker threads having state information;

a thread monitoring circuit perform;

estimating a retirement rate of a state associated with the worker threads; and

a thread dispatcher circuit perform;

detecting a context switch request,

in response to detecting the context switch request, perform;

determining, based upon the estimated state retirement rate associated with the worker threads and a rate of saving state of the worker threads, if the worker threads should be halted and the state of the worker threads saved to a memory, and

in response to the determining, halting and saving the state of the worker threads to the memory if the rate of saving is greater than the estimated state retirement rate, and wherein the rate of saving is determined based on a portion of a bandwidth available to write to the memory.

18. The apparatus of claim 17 wherein the thread dispatcher circuit that is further capable of:

if the rate of savings is not greater than the retirement rate,

allowing the worker threads to naturally retire, and

determining, based at least in part upon the state retirement rate of the worker threads, if the worker threads should be halted and the worker threads'"'"' state saved to memory.

19. The apparatus of claim 17 wherein, the thread monitoring circuit is further capable of:

monitoring the thread retirement rate of the threads; and

estimating the state retirement rate based at least in part upon the thread retirement rate.

20. The apparatus of claim 19, wherein the thread monitoring circuit is further capable of:

estimating the state retirement rate based at least in part upon the worker thread retirement rate by accounting for worker threads having variable size thread states.

21. The apparatus of claim 19 wherein, the thread monitoring circuit is further capable of thread scheduling.

22. The apparatus of claim 17, wherein the thread dispatcher circuit is further capable of:

based at least in part upon the estimation of state retirement rate, prioritizing the order in which worker threads will be halted and the worker threads'"'"' state saved.

23. The apparatus of claim 17 wherein the processor includes a single chip multiprocessor.

24. The apparatus of claim 23 wherein the processor includes a register state of at least 128 kilobytes.

25. A system comprising:

a processor executing a plurality of worker threads having state information;

a memory storing the state information of the worker threads when the threads are not being executed by the processor

a thread monitoring circuit perform;

estimating a retirement rate of a state associated with the worker threads; and

a thread dispatcher circuit perform;

detecting a context switch request,

in response to detecting the context switch request, determining, based upon the estimated state retirement rate associated with the worker threads and a rate of saving state of the worker threads, if the worker threads should be halted and the state of the worker threads saved to a memory, and

in response to the determining, halting and saving the state of the worker threads to the memory if the rate of saving is greater than the estimated state retirement rate, and wherein the rate of saving is determined based on a portion of a bandwidth available to write to the memory.

26. The system of claim 25 wherein the thread dispatcher circuit that is further capable of:

if the rate of savings is not greater than the retirement rate,

allowing the threads to naturally retire, and

determining, based at least in part upon the state retirement rate of the worker threads, if the worker threads should be halted and the worker threads'"'"' state saved to memory.

27. The system of claim 25, wherein the thread monitoring circuit is further capable of:

monitoring the thread retirement rate of the threads; and

estimating the state retirement rate based at least in part upon the thread retirement rate.

28. The system of claim 27, wherein the thread monitoring circuit is further capable of:

estimating the state retirement rate based at least in part upon the thread retirement rate by accounting for worker threads having variable size thread states.

29. The system of claim 27 wherein, the thread monitoring circuit is further capable of thread scheduling.

30. The system of claim 25, wherein the thread dispatcher circuit is further capable of:

based at least in part upon the estimation of state retirement rate, prioritizing the order in which worker threads will be halted and the worker threads'"'"' state saved.

31. The system of claim 25 wherein the processor includes a single chip multiprocessor.

32. The system of claim 31 wherein the processor includes a register state of at least 128 kilobytes.