Method and system for performing real-time operation

• US 20050066330A1
• Filed: 08/02/2004
• Published: 03/24/2005
• Est. Priority Date: 08/14/2003
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kanai, Tatsunori, Maeda, Seiji, Yano, Hirokuni, Yoshii, Kenichiro
• Granted Patent: US 7,464,379 B2
• Time in Patent Office: Days
• US Class Current: 718/102
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/324 by lowering clock frequency
• CPC Class Codes: G06F 1/3275 Power saving in memory, e.g. RAM, cache
• CPC Class Codes: G06F 1/3287 by switching off individual functional units in the computer system
• CPC Class Codes: G06F 1/329 by task scheduling
• CPC Class Codes: G06F 1/3296 by lowering the supply or operating voltage
• CPC Class Codes: G06F 9/4887 involving deadlines, e.g. rate based, periodic
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

An information processing system performs a real-time operation periodically at specific time intervals. The system includes a unit for performing a scheduling operation of assigning the real-time operation to a processor to perform the real-time operation periodically at the specific time intervals by the processor, a unit for computing a ratio of an execution time of the real-time operation to be performed by the processor at a first operating speed, based on the specific time intervals and cost information concerning a time required to perform the real-time operation by the processor at the first operating speed, and a unit for performing an operating speed control operation to operate the processor at a second operating speed that is lower than the first operating speed, the second operating speed being determined based on the computed ratio.

Claims

1. A method of performing a real-time operation periodically at specific time intervals, the method comprising:

performing a scheduling operation of assigning the real-time operation to a processor to perform the real-time operation periodically at the specific time intervals by the processor;

computing a ratio of an execution time of the real-time operation to be performed by the processor at a first operating speed to each of the specific time intervals, based on the specific time intervals and cost information concerning a time required to perform the real-time operation by the processor at the first operating speed; and

performing an operating speed control operation to operate the processor at a second operating speed that is lower than the first operating speed, the second operating speed being determined based on the computed ratio.

2. The method according to claim 1, wherein performing the operating speed control operation includes determining the second operating speed based on the first operating speed and the computed ratio, the second operating speed being determined to meet conditions that execution of the real-time operation in each of time periods corresponding to the specific time intervals is completed before a next one of the time periods starts.

3. The method according to claim 1, wherein performing the operating speed control operation includes controlling a frequency of a clock signal supplied to the processor to operate the processor at the second operating speed.

4. A method of performing a real-time operation including a plurality of chained tasks periodically at specific time intervals using a plurality of processors, the method comprising:

dividing the chained tasks into a plurality of task groups which are executable in parallel, based on a relationship among the tasks in order of task execution;

performing a scheduling operation of determining execution start timing of each of the task groups in each time period of time periods corresponding to the specific time intervals and one of the processors which executes a corresponding one of the task groups in the each time period;

selecting one of the task groups whose time interval from start of the each time period to completion of an execution time in the each time period is longest, based on the execution start timing of each of the task groups and cost information concerning a time required to execute each of the task groups by a corresponding one of the processors at a first operating speed;

computing a ratio of the time interval corresponding to the selected one of the task groups to each of the specific time intervals; and

performing an operating speed control operation to operate each of the processors at a second operating speed that is lower than the first operating speed, the second operating speed being determined based on the computed ratio.

5. The method according to claim 4, wherein performing the operating speed control operation includes determining the second operating speed based on the first operating speed and the computed ratio, the second operating speed being determined to meet conditions that execution of the selected one of the task groups in each of time periods corresponding to the specific time intervals is completed before a next one of the time periods starts.

6. The method according to claim 4, wherein performing the operating speed control operation includes controlling a frequency of a clock signal supplied to each of the processors to operate each of the processors at the second operating speed.

7. The method according to claim 4, wherein the dividing includes dividing the chained tasks into a first task group and a second task group based on a relationship among the tasks in order of task execution, the second task group being executed after the first task group, and performing the scheduling operation includes determining execution start timing of each of the first task group and the second task group in the each time period to periodically execute the first task group at the specific time intervals and periodically execute the second task group at the specific time intervals with a one-period delay relative to the first task group.

8. An information processing system which performs a real-time operation periodically at specific time intervals, the system comprising:

a processor;

means for performing a scheduling operation of assigning the real-time operation to the processor to perform the real-time operation periodically at the specific time intervals by the processor;

means for computing a ratio of an execution time of the real-time operation to be performed by the processor at a first operating speed to each of the specific time intervals, based on the specific time intervals and cost information concerning a time required to perform the real-time operation by the processor at the first operating speed; and

means for performing an operating speed control operation to operate the processor at a second operating speed that is lower than the first operating speed, the second operating speed being determined based on the computed ratio.

9. The information processing system according to claim 8, wherein the means for performing the operating speed control operation includes means for determining the second operating speed based on the first operating speed and the computed ratio, the second operating speed being determined to meet conditions that execution of the real-time operation in each of time periods corresponding to the specific time intervals is completed before a next one of the time periods starts.

10. The information processing system according to claim 8, wherein the means for performing the operating speed control operation includes means for controlling a frequency of a clock signal supplied to the processor to operate the processor at the second operating speed.

11. An information processing system which performs a real-time operation including a plurality of chained tasks periodically at specific time intervals, the system comprising:

a plurality of processors;

means for dividing the chained tasks into a plurality of task groups which are executable in parallel, based on a relationship among the tasks in order of task execution;

means for performing a scheduling operation of determining execution start timing of each of the task groups in each time period of time periods corresponding to the specific time intervals and one of the processors which executes a corresponding one of the task groups in the each time period;

means for selecting one of the task groups whose time interval from start of the each time period to completion of an execution time in the each time period is longest, based on the execution start timing of each of the task groups and cost information concerning a time required to execute each of the task groups by a corresponding one of the processors at a first operating speed;

means for computing a ratio of the time interval corresponding to the selected one of the task groups to each of the specific time intervals; and

means for performing an operating speed control operation to operate each of the processors at a second operating speed that is lower than the first operating speed, the second operating speed being determined based on the computed ratio.

12. The information processing system according to claim 11, wherein the means for performing the operating speed control operation includes means for determining the second operating speed based on the first operating speed and the computed ratio, the second operating speed being determined to meet conditions that execution of the selected one of the task groups in each of time periods corresponding to the specific time intervals is completed before a next one of the time periods starts.

13. The information processing system according to claim 11, wherein the means for performing the operating speed control operation includes means for controlling a frequency of a clock signal supplied to each of the processors to operate each of the processors at the second operating speed.

14. The information processing system according to claim 11, wherein the means for dividing includes means for dividing the chained tasks into a first task group and a second task group based on a relationship among the tasks in order of task execution, the second task group being executed after the first task group, and the means for performing the scheduling operation includes means for determining execution start timing of each of the first task group and the second task group in the each time period to periodically execute the first task group at the specific time intervals and periodically execute the second task group at the specific time intervals with a one-period delay relative to the first task group.

15. A program which is stored in a computer-readable media and cause a computer to perform a real-time operation periodically at specific time intervals, the program comprising:

causing the computer to perform a scheduling operation of assigning the real-time operation to a processor to perform the real-time operation periodically at the specific time intervals by the processor;

causing the computer to compute a ratio of an execution time of the real-time operation to be performed by the processor at a first operating speed to each of the specific time intervals, based on the specific time intervals and cost information concerning a time required to perform the real-time operation by the processor at the first operating speed; and

causing the computer to perform an operating speed control operation to operate the processor at a second operating speed that is lower than the first operating speed, the second operating speed being determined based on the computed ratio.

16. A program which is stored in a computer-readable media and cause a computer to perform a real-time operation including a plurality of chained tasks periodically at specific time intervals using a plurality of processors, the program comprising:

causing the computer to divide the chained tasks into a plurality of task groups which are executable in parallel, based on a relationship among the tasks in order of task execution;

causing the computer to perform a scheduling operation of determining execution start timing of each of the task groups in each time period of time periods corresponding to the specific time intervals and one of the processors which executes a corresponding one of the task groups in the each time period;

causing the computer to select one of the task groups whose time interval from start of the each time period to completion of an execution time in the each time period is longest, based on the execution start timing of each of the task groups and cost information concerning a time required to execute each of the task groups by a corresponding one of the processors at a first operating speed;

causing the computer to compute a ratio of the time interval corresponding to the selected one of the task groups to each of the specific time intervals; and

causing the computer to perform an operating speed control operation to operate each of the processors at a second operating speed that is lower than the first operating speed, the second operating speed being determined based on the computed ratio.

17. The program according to claim 16, wherein causing the computer to divide includes causing the computer to divide the chained tasks into a first task group and a second task group based on a relationship among the tasks in order of task execution, the second task group being executed after the first task group, the second task group being executed after the first task group, and causing the computer to perform the scheduling operation includes causing the computer to determine execution start timing of each of the first task group and the second task group in the each time period to periodically execute the first task group at the specific time intervals and periodically execute the second task group at the specific time intervals with a one-period delay relative to the first task group.

18. An information processing system which performs a real-time operation periodically at specific time intervals, the system comprising:

a first processor;

a second processor which performs a scheduling operation of assigning the real-time operation to the first processor to perform the real-time operation periodically at the specific time intervals by the first processor, and computes a ratio of an execution time of the real-time operation to be performed by the first processor at a first operating speed to each of the specific time intervals, based on the specific time intervals and cost information concerning a time required to perform the real-time operation by the first processor at the first operating speed; and

a speed control unit configured to perform an operating speed control operation to operate the first processor at a second operating speed that is lower than the first operating speed, the second operating speed being determined based on the computed ratio.