Overview of real-time scheduling problems

Abstract

Introduction A computerized real-time system is required to complete its work on a timely basis. Typical applications are digital control, command and control, signal processing and communication systems. The aim of real-time scheduling is to build-up a sequence of jobs that meets hard timing constraints at run-time. In opposition with the classical scheduling literature, real-time scheduling is not necessarily on-line scheduling. The main characteristic of real-time systems is the behavioral predictability. Timing constraints will be met whatever happens in the system. Real-time operating systems define recurring tasks. Real-time tasks are often periodically released. Basically, a periodic task gets its input data from sensors and command the controlled process by sending data to actuators. Every execution of a task is called a job. In the general model of periodic tasks, a task # i is defined by an o#set O i , that defines the release time of its first job; its worst-case execution