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Gurwinder Kaur, Lovely Professional University Unit 14: Advance Priority-driven Scheduling of Periodic Tasks

Unit 14: Advance Priority-driven Notes
Scheduling of Periodic Tasks

CONTENTS
Objectives
Introduction

14.1 Sufficient Schedulability Conditions for the RM and DM Algorithms
14.1.1 Schedulable Utilization of the RM (Di= pi)
14.1.2 Schedulable Utilization of the RM
14.1.3 Enhanced Schedulable Utilization

14.1.4 Schedulable Utilization of the RM Algorithm for Multi-frame Tasks
14.2 Practical Factors
14.2.1 Blocking and Priority Inversion
14.2.2 Self-Suspension and Context Switches

14.2.3 Tick Scheduling
14.3 Summary
14.4 Keywords
14.5 Review Questions

14.6 Further Readings

Objectives

After studying this unit, you will be able to:
 Define Sufficient Schedulability conditions for the RM Algorithms

 Describe Sufficient Schedulability conditions for the DM Algorithms
 Analyse Practical Factors

Introduction

In case of global scheduling, we can divide schedulers in different groups. This division depends
on the priority consumed by task during its execution. If a task priority cannot change during
the entire lifetime of task, the algorithm of scheduling consists of “fixed task priority”. In case
the priority can change only at job boundaries, for example with EDF, and then the algorithm is
said to have “fixed job priority”. In case the priority can change throughout the job execution
also, and then the algorithm is said to have “dynamic priority”. In this unit, we will discuss the
concept of Sufficient Schedulability conditions for the RM and DM Algorithms.

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