Functional Parameter & Scheduling Hierarchy | Real Time System

Functional Parameter ampScheduling Hierarchy

BY

Aananda Bhandari

Shubham Ghimire1

Functonal Parameter

bull Preemptivity Of Jobs

bull Criticality Of Jobs

bull Optional Execution

bull Laxity Type And Laxity Function

2

Preemptivity Of Jobs

bull Preemptable Job - Can be suspended and resumed from the suspention point

bull Example - Computations

bull Non-preemptable - Data transmission

3

Criticality Of Jobs

bull Criticality of job - Positive number indicating how critical the job is

bull Increases with importance of job

bull Donrsquot use the terms priority and weight

4

Optional Executions

bull If an optional job or optional portion completes late or is not executed at all the system still functions satisfactorily

bull Non-optional job - Mandatory

5

Laxity Type amp Laxity Functions

bull Laxity type- indicates whether the job is hard or soft

bull Hard RT Jobs- ldquoBetter never than laterdquo

bull Soft RT Jobs- Usefulness decreases gradually

6

Resource Parameters Of Jobs amp Parameters Of Job Resources

bull Preemptivity Of Resources

bull Resource Graph

7

Preemptivity Of Resources

bull Describing processors and resources independently of application Parameter of resources Preemptivity

bull Nonpreemptable resource Each unit is to be used serially

8

Resource Graph

bull Configuration of the resources

bull Vertex Ri for every processor or resource Ri in the system

bull Attributes of the vertex are the parameters of the resource

bull P- processors R- for passive resources

bull Parametersndash Type

ndash Number of available units

9

Scheduling Hierrarchy

10

Scheduling Hierarchy

bull Task Graphndash Representation of application system

ndash Processor time

ndash Resource requirement

ndash Timing constraints amp dependencies of jobs

bull Resource Graphndash Amount of available resources

ndash Resource attributes

ndash Usage rules

bull Scheduling and resource access-control algorithms used by the operating system

11

Scheduler amp Schedules

bull Scheduler

ndash implements scheduling algorithms

ndashSchedules Jobs

ndashAllocates Resources

Example Processors assignment on jobs (or vice versa)

bull Schedule Assignment of all system jobs on available processors produced by the scheduler

12

Valid Schedule

bull Every processor assigned to at most one job at any time

bull Every job is assigned at most one processor at any time

bull No job is scheduled before its release-time

bull Total amount of processor time = execution time

bull Precedence and resource usage constraints are satisfied

13

Feasibility Optimality amp Performance Measures

bull valid schedule is a feasible schedule if every job completes by its deadline

bull Hard RTS scheduling algorithm is optimal if (using) the algorithm (the scheduler) always produces a feasible schedule if the given set of jobs has feasible schedules

bull Lateness tardiness miss loss and invalid rates

14

Thank You

15

Reference Real-Time Systems Jane W S Liu

Functonal Parameter

bull Preemptivity Of Jobs

bull Criticality Of Jobs

bull Optional Execution

bull Laxity Type And Laxity Function

2





3

Criticality Of Jobs




4

Optional Executions



5





6



bull Resource Graph

7




8

Resource Graph







9


10








ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15






3

Criticality Of Jobs




4

Optional Executions



5





6



bull Resource Graph

7




8

Resource Graph







9


10








ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15


Criticality Of Jobs




4

Optional Executions



5





6



bull Resource Graph

7




8

Resource Graph







9


10








ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15


Optional Executions



5





6



bull Resource Graph

7




8

Resource Graph







9


10








ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15






6



bull Resource Graph

7




8

Resource Graph







9


10








ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15




bull Resource Graph

7




8

Resource Graph







9


10








ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15





8

Resource Graph







9


10








ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15


Resource Graph







9


10








ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15



10








ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15









ndash Usage rules


11


bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15



bull Scheduler


ndashSchedules Jobs




12

Valid Schedule






13





14

Thank You

15


Valid Schedule






13





14

Thank You

15






14

Thank You

15


Thank You

15


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