Thomas Ralya

A practitioner's handbook for real-time analysis

Preface. Part 1: Introduction. 1. About this Handbook. 2. Fundamentals of RMA. Part 2: Concepts and Techniques. 3. A Framework for Describing Real-Time Systems. 4. Techniques for Analyzing Timing Behavior. Part 3: Analyzing Real-Time Systems. 5. Basic Real-Time Situations. 6. Advanced Real-Time Situations. 7. Effects of Operating System and Runtime Services on Timing Analysis. Part 4: Using the Handbook on Realistic Systems. 8. Analyzing Complex Systems. 9. Designing with Rate Monotonic Analysis. Part 5: Appendices. A. Rules of Thumb. B. Notation Used in this Handbook. C. Bibliography. D. Glossary. E. Index.

Analyzing Complex Systems

This chapter illustrates how this handbook can be used to analyze the timing behavior of a complex real-time system. In this chapter, we present a case study of a single processor within a distributed message passing system.

Designing with Rate Monotonic Analysis

This chapter illustrates how the principles of RMA can be used while designing a real-time system. In this chapter, we present a case study derived from an active sonar system.

Effects of Operating System and Runtime Services on Timing Analysis

This chapter describes the effects of operating systems and runtime system services on the timing analysis of real-time systems. In most of the real-time situations described in Part 3 of this book, we have not considered the effects of the operating system or the runtime system on which the application runs. However, this underlying software can have important effects on the timing behavior of the system. It is important to be able to identify and evaluate these effects and to know when they must be included in the real-time analysis of a system.

A Framework for Describing Real-Time Systems

This chapter describes a framework for considering the timing and concurrency aspects of real-time systems. Our goals in this chapter are To develop a framework that is independent of the various application domains. To create a common vocabulary for articulating timing characteristics of systems. To offer a way of classifying different types of resource allocation problems from a timing point of view.

Basic Real-Time Situations

The real-time situations in this chapter have these properties in common: Fixed-priority scheduling with no operating system overhead. We have perfect preemption; that is, when a task “ wakes up” from its suspension, it either has a higher priority than the currently executing task and thus preempts it instantaneously, or has a lower priority and is instantaneously placed into the task-ready queue. CPU and data are the only resources under contention. Real-time situations are confined to a uniprocessor.

Fundamentals of RMA

The purpose of this chapter is to review briefly the fundamental principles and methods of RMA. We assume that you have prior knowledge of RMA and require only a refresher. If you require more than a refresher, please contact the Software Engineering Institute (SEI), Customer Relations (see page P-3), for information about RMA tutorials, or see the papers listed in the “Bibliography.” In particular, Sha and Goodenough provide a basic introduction to the principles of RMA [Sha 90a].

Advanced Real-Time Situations

The following table lists the groups of real-time situations in this chapter and shows the page numbers on which they are located: Group Page Number Group 4 Controlling Jitter page 6-2 Group 5 Message Passing Paradigms page 6-64 Group 6 Issues in Multiprocessor and Distributed Systems page 6-94

About This Handbook

In general, we assume that the reader has at least some experience (three to five years) as a real-time system developer and has had some previous exposure to rate monotonic analysis (RMA). We include a refresher on the principles of RMA in Chapter 2, “Fundamentals of RMA.” Further information about RMA can be obtained from the publications listed in the bibliography, and there are companies that provide tutorial introductions and training in RMA.