Object-Oriented Design and Implementation of the OE-Scheduler in Real-time Environments

1
Object-Oriented Design and Implementation of the
OE-Scheduler in Real-time Environments

• Ilhyun Lee
• Cherry K. Owen
• Haesun K. Lee
• The University of Texas of the Permian Basin

2
Outline

• Introduction
• Motivation and Objective
• UML Diagram for OE-Scheduler
• Implementation for OE-Scheduler
• Conclusion
• Future Work

3
Introduction

• Real-Time System
• Periodic Task Model
• Object Oriented Design
• OE-Scheduler

4
Real-Time System

• Computing system with a set of execution models
  that have timing constraints
• Hard Real-Time System
• Soft Real-Time System

5
Hard Real-Time System
6
Soft Real-Time System
7
Periodic Task Model

• A sequence of the same type of event occurring at
  constant intervals
• Task scheduling entity
• Event recurring instance of scheduling entity

8
Object Oriented Design

• Problems are modeled using objects
• The object-oriented approach has the potential to
  reduce complexity, improve flexibility, and
  reduce expenses
• Object reusability

9
OE-Scheduler

• Scheduler that generates a schedule of periodic
  tasks by the principle of eliminating unnecessary
  context switches under the rate monotonic
  algorithm
• Guarantee the hard deadlines of an arbitrary
  number of periodic tasks in hard real-time
  environments
• Object-oriented design

10
Motivation

• Future real-time system will run in highly
  dynamic behavior environments
• Current our procedural scheduling algorithms
  cannot be efficiently applied to future real-time
  system
• This observation motivated us to work on
  developing an object-oriented view-point of the
  OE-scheduler in hard real-periodic environments

11
Objective

• Developing an object-oriented view-point of the
  OE-scheduler that generates a schedule of
  periodic tasks by the principle of eliminating
  unnecessary context switches under the rate
  monotonic algorithm in hard real-periodic
  environments

12
UML Diagram for OE-Scheduler

• Class Diagram for OE-Scheduler
• Sequence Diagram to Produce a OE-Schedule

13
Class Diagram for OE-Scheduler
14
Sequence Diagram to Produce a OE-Schedule
15
Implementation for OE-Scheduler

• Scheduling algorithm for OE-Scheduler
• Test result of the object-oriented OE-Scheduler
• Comparison table

16
Scheduling Algorithm for OE-Scheduler

• Step1. If Pij i 1..n, j 0..n arrives the
  system at the same time, pick the highest
  priority event of Pij i 1..n, j 0..n.
  Determine the Current Request Period (CRP) of the
  selected event.

17
Scheduling Algorithm for OE-Scheduler

• Step2. If the CRP of the selected event is odd,
  then go to Step3. Otherwise, if the CRP of the
  selected event is even, then calculate the Slack,
  the maximum amount of time that a scheduler can
  delay running the task without missing its
  current deadline, for the selected event. Delay
  the execution of the selected event until the
  Slack of the selected event becomes empty. When
  the Slack of the selected event becomes empty,
  schedule the selected event under the Rate
  Monotonic Algorithm. Go to Step4

18
Scheduling Algorithm for OE-Scheduler

• Step3. Immediately schedule the selected event
  under the Rate Monotonic Algorithm.
• Step4. Go to Step1 until the final event is
  processed

19
Scheduling Algorithm for OE-Scheduler
20
Test Result of the Object-oriented OE-Scheduler

• Record structure of the periodic task
• Workload file OE-schedule.txt
• Menu-based user interface
• The scheduling points with CRP
• Schedule for 4 periodic task by OE-Scheduler

21
Record Structure of the Periodic Task Workload
22
Workload File OE-schedule.txt
23
Menu-based User Interface
24
The Scheduling Points with CRP
25
Schedule for 4 Periodic Task by OE-Scheduler
26
Schedule for 4 periodic task by OE-Scheduler
27
Comparison Table
28
Conclusion

• A study of dynamic behavior property in hard
  real-time environments
• Robust design facilitates easier extension of the
  system to include more dynamic environments
• Provide the real-time system engineers with
  greater flexibility to design future real-time
  systems
• Helping the designer of real-time operating
  systems

29
Future Work

• Extend our scheduling algorithms to distributed
  and multiprocessor environments