CPU usage regulation

1. A method of calculating central processing unit (CPU) usage by a given task, the method comprising the steps of:

associating the given task with a top level class and a sub-class, the sub-class being one of a plurality of sub-classes directly associated with a parent class; and

determining a target CPU usage for the given task from a weight associated with the sub-class representing a relative share of a target CPU usage associated with the parent class and a target CPU usage associated with the top level class;

wherein the step of determining the target CPU usage for the given task comprises the steps of:

forming a quotient by dividing the weight associated with the sub-class by a sum of weights associated with the plurality of sub-classes directly associated with the parent class; and

multiplying the target CPU usage associated with the parent class by the quotient.

2. The method of claim 1 further comprising:

determining an actual usage of said CPU by said given task in a first predetermined evaluation interval;

determining a penalty duration for said given task based on said actual usage and said target CPU usage for said given task; and

applying a penalty to said given task for said penalty duration during a second predetermined evaluation interval.

3. The method of claim 2 wherein said applying said penalty comprises demoting a scheduling priority associated with said given task.

4. The method of claim 2 wherein said penalty is applied continuously for said penalty duration.

5. The method of claim 2 wherein said penalty is applied during a plurality of periods over said second predetermined evaluation interval, such that a total duration of application of said penalty is equivalent to said penalty duration.

6. The method of claim 2 wherein said actual usage of said CPU by said given task in said first predetermined evaluation interval is a first actual usage and said penalty duration based on said first actual usage is a first penalty duration, said method further comprising:

determining a second actual usage of said CPU by said given task in said second predetermined evaluation interval;

determining a second penalty duration for said given task based on said second actual usage and said target CPU usage for said given task; and

applying said penalty to said given task for said second penalty duration during a third predetermined evaluation interval.

7. The method of claim 1 , wherein the top level class is the parent class of the sub-class.

8. The method of claim 1 , wherein a further sub-class of the top level class is the parent class of the sub-class.

9. A scheduler for execution in a kernel of a central processing unit (CPU), the scheduler containing data and instructions stored in a computer readable medium to enable tasks to be scheduled for execution by the kernel, the data and instructions allowing the scheduler to perform a method comprising the steps of:

associating a given task with a top level class and a sub-class, the sub-class being one of a plurality of sub-classes directly associated with a parent class; and

determining a target CPU usage for the given task from a weight associated with the sub-class representing a relative share of a target CPU usage associated with the parent class and a target CPU usage associated with the top level class;

wherein the step of determining the target CPU usage for the given task comprises the steps of:

forming a quotient by dividing the weight associated with the sub-class by a sum of weights associated with the plurality of sub-classes directly associated with the parent class; and

multiplying the target CPU usage associated with the parent class by the quotient.

10. The scheduler of claim 9 , wherein the method further comprises the steps of:

determining an actual usage of the CPU by the given task in a first predetermined evaluation interval;

determining a penalty duration for the given task based on the actual usage and the target CPU usage for the given task; and

applying a penalty to the given task for the penalty duration during a second predetermined evaluation interval.

11. The scheduler of claim 10 , wherein the step of applying the penalty comprises demoting a scheduling priority associated with the given task.

12. The scheduler of claim 10 , wherein the penalty is applied continuously for the penalty duration.

13. The scheduler of claim 10 , wherein the penalty is applied during a plurality of periods over the second predetermined evaluation interval, such that a total duration of application of the penalty is equivalent to the penalty duration.

14. The scheduler of claim 10 , wherein the actual usage of the CPU by the given task in the first predetermined evaluation interval is a first actual usage and the penalty duration based on the first actual usage is a first penalty duration, the method further comprising the steps of:

determining a second actual usage of the CPU by the given task in the second predetermined evaluation interval;

determining a second penalty duration for the given task based on the second actual usage and the target CPU usage for the given task; and

applying the penalty to the given task for the second penalty duration during a third predetermined evaluation interval.

15. A computer readable medium containing computer-executable instructions that, when performed by an apparatus for calculating usage of a central processing unit (CPU) in a kernel, cause the apparatus to:

associate a given task with a top level class and a sub-class, the sub-class being one of a plurality of sub-classes directly associated with a parent class; and

determine a target CPU usage for the given task from a weight associated with the sub-class representing a relative share of a target CPU usage associated with the parent class and a target CPU usage associated with the top level class;

wherein the step of determining the target CPU usage for the given task comprises the steps of:

forming a quotient by dividing the weight associated with the sub-class by a sum of weights associated with the plurality of sub-classes directly associated with the parent class; and

multiplying the target CPU usage associated with the parent class by the quotient.

16. The computer readable medium of claim 15 , further containing computer-executable instructions that, when performed by the apparatus for calculating usage of the central processing unit (CPU) in the kernel, further cause the apparatus to:

determine an actual usage of the CPU by the given task in a first predetermined evaluation interval;

determine a penalty duration for the given task based on the actual usage and the target CPU usage for the given task; and

apply a penalty to the given task for the penalty duration during a second predetermined evaluation interval.

17. The computer readable medium of claim 16 , wherein applying the penalty comprises demoting a scheduling priority associated with the given task.

18. The computer readable medium of claim 16 , wherein the penalty is applied continuously for the penalty duration.

19. The computer readable medium of claim 16 , wherein the penalty is applied during a plurality of periods over the second predetermined evaluation interval, such that a total duration of application of the penalty is equivalent to the penalty duration.

20. The computer readable medium of claim 16 , wherein the actual usage of the CPU by the given task in the first predetermined evaluation interval is a first actual usage and the penalty duration based on the first actual usage is a first penalty duration, the computer readable medium further containing computer-executable instructions that, when performed by the apparatus for calculating usage of the central processing unit (CPU) in the kernel, further cause the apparatus to

determine a second actual usage of the CPU by the given task in the second predetermined evaluation interval;

determine a second penalty duration for the given task based on the second actual usage and the target CPU usage for the given task; and

apply the penalty to the given task for the second penalty duration during a third predetermined evaluation interval.