Page 54 - DCAP608_REAL TIME SYSTEMS

Gurwinder Kaur, Lovely Professional University Unit 5: Real-time System Dependencies

Unit 5: Real-time System Dependencies Notes

CONTENTS
Objectives
Introduction

5.1 Other Types of Dependencies
5.2 Functional Parameters
5.3 Resource Parameters of Jobs and Parameters of Resources

5.3.1 Pre-emptivity of Resources
5.3.2 Resource Graph
5.4 Scheduling Hierarchy
5.4.1 Feasibility, Optimality and Performance Measures
5.5 Summary

5.6 Keywords
5.7 Review Questions
5.8 Further Readings

Objectives

After studying this unit, you will be able to:
 Discuss the Types of Dependencies
 Explain the Functional Parameters
 Define the Resource Parameters of Job

 Analyse Parameters of Resources
 Enumerate Hierarchy Scheduling

Introduction

Tasks often have explicit dependencies specified among themselves, implicit dependencies are
more common. Tasks might become inter-dependent for several reasons. A common form of
dependency arises when one task needs the results of another task to proceed with its
computations. The positional error computation task can meaningfully run only after the “current
position determination” task completes. Further, even when no explicit data exchanges are
involved, tasks might be required to run in certain order. Dependency among tasks severely
restricts the applicability of the results on task scheduling. The reason is that EDF and RMA
schedulers impose no constraints on the order in which various tasks execute. Schedules produced
by EDF or RMA might violate the constraints imposed due to task dependencies. In this unit, we
will discuss real-time system dependencies.

5.1 Other Types of Dependencies

In this section, we will discuss some other types of dependencies.

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