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Real-Time Systems Scheduling Tool Development

Abstract

This paper presents a real-time system (RTS) scheduling tool which implements some of the most popular scheduling algorithms. It allows users to specify real-time tasks in a RTS, then evaluates task scheduleability and plots the simulated schedules. It can be used by both instructors and students of RTS classes.

1. Introduction

Real-time systems are those systems that are required to respond to an external event in some timely manner6,8. An RTS is always subjected to timing constraints. The timing constraints imposed on hard real-time systems are absolute and must be satisfied. Therefore, special consideration needs to be taken when designing how a real-time system will execute all the possible tasks it may be assigned over any period of time.

RTS scheduling is a critical, and perhaps the most important part in teaching a real-time system class. Dozens of well-known scheduling algorithms are introduced in many textbooks7,4, but can sometimes be difficult to explain with just words and graphs. It is desirable that, given a set of real-time task specifications, we have a dedicated software tool to carry out scheduleability analysis and schedule generation. However, such tools are not yet available. Commercial real- time operating system products, such as VxWorks9, provide logic instruments with a graphical view of schedules, but they only work with a fully developed RTS - not a RTS model in terms of task specifications.

This paper presents a RTS scheduling tool newly developed at the Software Engineering Department of Monmouth University. The tool implements some of the most popular RTS scheduling algorithms, such as Earliest Deadline First (EDF), Least Slack Time First (LST), and Deadline Monotonic (DM). The tool evaluates RTS task scheduleability and plots the simulated scheduling results. It also comes with a very friendly user interface which allows users to easily (1) add or delete tasks/jobs, (2) specify or modify the real-time parameters of tasks/jobs, (3) select tasks/jobs for scheduling, and (4) select scheduling algorithms. For periodic tasks, the tool automatically calculates the hyperperiod and plots the schedule for one hyperperiod. As jobs are pre-empted and move to a waiting state, the tool displays the jobs in a waiting queue over the entire scheduling simulation.

The tool is developed primarily for education purpose. It is helpful for both instructors and students: First, it allows instructors to illustrate as many scheduling examples as possible during the limited class hours by simply changing the RTS tasks/jobs set or their real-time parameters. Second, it helps students to understand how the scheduling process proceeds with a given scheduling algorithm. Third, but not least, it allows students to compare and contrast the scheduling results of a given RTS model with different scheduling algorithms. As students are assigned various scheduling exercises, the RTS scheduling tool helps to reinforce the scheduling algorithm concepts they have learned by providing the correct schedules and the schedules’

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Wang, J., & Ghiringhelli, D. (2006, June), Real Time Systems Scheduling Tool Development Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. 10.18260/1-2--1068