Improvement to Quick Processor-Demand Analysis for EDF-Scheduled Real-Time Systems

Earliest Deadline First (EDF) is an optimal scheduling algorithm for uniprocessor real-time systems. Quick Processor-demand Analysis (QPA) provides efficient and exact schedulability tests for EDF scheduling with arbitrary relative deadline. In this paper, we propose Improved Quick Processor-demand Analysis (QPA*) which is based on QPA. By extensive experiments, we show that QPA* can significantly reduce the required calculations to perform an exact test for unschedulable systems. We prove that the computation time for testing schedulable systems is hardly affected. Hence the required calculations for general systems can be significantly decreased.

1. Introduction

The most important attribute of real-time systems is that the correctness of such systems depends on not only the running results but also on the time at which results are produced. Real-time systems have to guarantee that all the strict timing requirements must be satisfied. In other words, real-time systems have timing requirements that must be guaranteed. Scheduling and schedulability analysis enables these guarantees to be provided.