Wake-and-go mechanism with prioritization of threads

• US 8,171,476 B2
• Filed: 02/01/2008
• Issued: 05/01/2012
• Est. Priority Date: 02/01/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Arimilli, Ravi K., Sharma, Satya P., Swanberg, Randal C.
• Primary Examiner(s): CAO, DIEM K
• Application Number:
  US12/024,669
• Publication Number:
  US 20110173625A1
• Time in Patent Office: 1,551 Days
• Field of Search: 718/103, 718/102, 711/163, 711/108, 719/313, 719/314
• US Class Current: 718/102
• CPC Class Codes: G06F 9/4843 by program, e.g. task dispatcher, supervisor, operating system

Abstract

A hardware private array is a thread state storage that is embedded within the processor or within logic associated with a bus or wake-and-go logic. The hardware private array and/or wake-and-go array may have a limited storage area. Therefore, each thread may have an associated priority. If there is insufficient space in the hardware private array, then the wake-and-go mechanism may compare the priority of the thread to the priorities of the threads already stored in the hardware private array and wake-and-go array. If the thread has a higher priority than at least one thread already stored in the hardware private array and wake-and-go array, then the wake-and-go mechanism may remove a lowest priority thread, meaning the thread is removed from hardware private array and wake-and-go array and converted to a flee model.

Claims

1. A method, in a data processing system, for performing a wake-and-go operation, the method comprising:

detecting a current thread that is waiting for an event that modifies a data value associated with a target address;

determining whether there is data associated with a lower priority thread in a hardware private array of the data processing system, wherein the hardware private array cannot be addressed by an operating system or work threads running on a processor, wherein the lower priority thread is a thread having a lower priority than a priority of the current thread;

in response to a determination that there is a lower priority thread in the hardware private array, removing data associated with the lower priority thread from the hardware private array and a wake-and-go storage array;

storing thread state information for the current thread in the hardware private array;

populating the wake-and-go storage array with the target address;

placing the current thread in a sleep state; and

responsive to the event that modifies the data value associated with the target address, reloading the thread state information from the hardware private array and placing the current thread in a non-sleep state.

2. The method of claim 1, further comprising:

determining whether-there-is sufficient space in the hardware private array for thread state information for the current thread, wherein the determination as to whether there is a lower priority thread in the hardware private array is performed in response to a determination that there is insufficient space in a hardware private array for thread state information for the current thread.

3. The method of claim 1, wherein the wake-and-go array is a content addressable memory and an address appearing on the bus is used to address the content addressable memory.

4. The method of claim 1, wherein the hardware private array comprises a plurality of memory cells embodied within a processor.

5. The method of claim 1, further comprising:

detecting the event that modifies the data value associated with the target address on a bus.

6. The method of claim 5, wherein the hardware private array is embodied within pervasive logic associated with the bus.

7. The method of claim 1, wherein the hardware private array is embodied within pervasive logic associated with the wake-and-go storage array.

8. The method of claim 1, wherein the hardware private array is a reserved portion of system memory.

9. The method of claim 8, further comprising:

requesting an additional portion of system memory to be reserved for the hardware private array.

10. The method of claim 1, further comprising:

converting the lower priority thread to a flee model.

11. The method of claim 1, further comprising:

if there is not a lower priority thread in the hardware private array, converting the current thread to a flee model.

12. The method of claim 1, wherein priority is determined based on a priority parameter associated with each thread.

13. The method of claim 1, wherein priority is determined based on staleness.

14. A data processing system, comprising:

a wake-and-go mechanism implemented in hardware;

a hardware private array; and

a wake-and-go array,

wherein the wake-and-go mechanism is configured to;

detect a current thread that is waiting for an event that modifies a data value associated with a target address;

determine whether there is data associated with a lower priority thread in the hardware private array of the data processing system, wherein the hardware private array cannot be addressed by an operating system or work threads running on a processor, wherein the lower priority thread is a thread having a lower priority than a priority of the current thread;

in response to a determination that there is a lower priority thread in the hardware private array, remove data associated with the lower priority thread from the hardware private array and a wake-and-go storage array;

store thread state information for the current thread in the hardware private array;

populate the wake-and-go storage array with the target address;

place the current thread in a sleep state; and

responsive to the event that modifies the data value associated with the target address, reload the thread state information from the hardware private array and place the current thread in a non-sleep state.

15. The data processing system of claim 14, wherein the wake-and-go mechanism is further configured to:

determine whether there is sufficient space in the hardware private array for thread state information for the current thread, wherein the determination as to whether there is a lower priority thread in the hardware private array is performed in response to a determination that there is insufficient space in a hardware private array for thread state information for the current thread.

16. The data processing system of claim 14, wherein the hardware private array is a reserved portion of system memory.

17. The data processing system of claim 16, wherein the wake-and-go mechanism is further configured to request an additional portion of system memory to be reserved for the hardware private array.

18. The data processing system of claim 14, wherein the wake-and-go mechanism is further configured to convert the lower priority thread to a flee model.

19. The data processing system of claim 14, wherein priority is determined based on a priority parameter associated with each thread or staleness.

20. A computer program product comprising a non-transitory computer useable medium having a computer readable program, wherein the computer readable program, when executed on a computing device, causes the computing device to:

detect a current thread that is waiting for an event that modifies a data value associated with a target address;

determine whether there is data associated with a lower priority thread in a hardware private array of the data processing system, wherein the hardware private array cannot be addressed by an operating system or work threads running on a processor, wherein the lower priority thread is a thread having a lower priority than a priority of the current thread;

in response to a determination that there is a lower priority thread in the hardware private array, remove data associated with the lower priority thread from the hardware private array and a wake-and-go storage array;

store thread state information for the current thread in the hardware private array;

populate the wake-and-go storage array with the target address;

place the current thread in a sleep state; and

responsive to the event that modifies the data value associated with the target address, reload the thread state information from the hardware private array and place the current thread in a non-sleep state.