Limited Busy Periods in Response Time Analysis for Tasks Under Global EDF Scheduling

Response time analysis (RTA) is a kind of effective methods to test the schedulability of real-time tasks under the global earliest deadline first (G-EDF) scheduling. The main idea of the RTA methods is to judge the schedulability of the task set by comparing the worst-case response time (WCRT) and deadline of each task. For obtaining a safe WCRT, existing RTA methods assume that the response times of carry-in jobs are equal to the WCRTs of the tasks generating these jobs. This assumption causes the low accuracy of existing RTA methods, since the busy period lengths of carry-in jobs are usually limited and the response times of these jobs thus cannot always reach the assumed WCRTs. This article proposes a new RTA method that has a higher accuracy than existing RTAs. The main idea of the new method is to limit the busy period lengths of carry-in jobs in the WCRT calculation. We also propose an efficiency improvement scheme for the new method. A set of experiments is conducted to evaluate the performances of the new method and the efficiency improvement scheme. The experimental results show that the new method has a higher acceptance ratio than the state-of-the-art RTA methods and the efficiency improvement scheme can significantly reduce the execution time of the new method.