RealTime Systems Scheduling Tool

1
Real-Time Systems Scheduling Tool

• Developed by
• Daniel Ghiringhelli
• Advisor Professor Jiacun Wang
• December 19, 2005

2
Overview

• Motivation
• Features
• Platform and Tools
• Software Engineering Approach
• Algorithm Overview (bonus included!)
• Tool Design (30,000 ft. view)
• Tool Overview and Demonstration
• Summary

3
Motivation

• Real-time systems time critical systems
• Schedule assignment of jobs to available
  processors
• Feasible schedule every job completes by its
  deadline
• Scheduling algorithms
• Clock driven / Round-robin /Priority-driven
• Need a tool to illustrate how these algorithms
  work
• Particularly in RTS classes
• and find feasible schedules
• Helpful for research

4
Features

• Common Priority-Driven Algorithm Support
• Earliest Deadline First
• Deadline Monotonic
• Least Slack First
• Hyperperiod calculation
• Extendable interface
• Simulations based on task specifications
• Graphical user interface
• Task management
• Visualization of a dynamic scheduler

5
Platform and Tools

• Written in Java
• Eclipse 3.0 IDE
• SWT GUI library
• Deployed as an executable JAR

Integrated JUnit Testing
6
Software Engineering Principles

• Informal process
• Frequent Releases
• GUI Mock-up
• Test Driven
• Regression TestPolicy

Initial Mock-up
7
Software Engineering Approach

• Lightweight V-Model approach
• Essentially a waterfall but with User Involvement
• No system testing (i.e., Lightweight)
• Test Driven
• UAT written during Requirements
• Unit Tests written during detailed design and
  construction
• Customer Checkpoints

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Lightweight V-Model
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Algorithms Overview DM

• Deadline Monotonic (DM)
• Static fixed priority scheduler
• Immediately pre-empts any running task with a
  higher priority task
• Advantages
• Easy to implement (most widely used)
• Low system overhead
• Disadvantages
• Not optimal
• Requires static prioritization before run-time

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Algorithm Overview EDF

• Earliest Deadline First (EDF)
• Dynamic priority scheduler
• Highest priority is assigned to the task with the
  nearest deadline
• Advantages
• EDF theoretically superior to DM
• Guaranteed scheduleability if CPU utilization
  100 or less
• Disadvantages
• More difficult to implement
• Higher system overhead
• Overloaded system is unpredictable (non-critical
  tasks may be scheduled before critical tasks)

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Algorithm Overview LSTF (bonus!)

• Least Slack Time First (LSTF)
• Dynamic priority scheduler
• Highest priority given to the task with the least
  slack time (timeToDeadline executionTimeLeft)
• Advantages
• Same as EDF
• Intuitively logical
• Disadvantages
• Same as EDF

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EDF and DM Example
T1(0, 5, 3, 5), T2(0, 3, 1, 3)
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RTS Scheduling Tool Design

• MVC Architecture
• Controlling thread polls simulation thread for
  model updates

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RTS Scheduling Tool Package View
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Thread Interaction
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Simulator Internals
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Tool Overview Demo
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Concluding Remarks

• RTS Scheduling Tool features
• Friendly UI
• Effective teaching tool
• Scheduleability analysis
• Work to be done
• Additional algorithms can be easily added!
• GUI features and options

19
Acknowledgments

• MU Software Engineering Faculty
• Professor Wang
• Professor McDonald