Double-Loop Feedback-Based Scheduling Approach for Distributed Real-Time Systems

The use of feedback control techniques has been gaining importance in real-time scheduling as a means to provide predictable performance in the face of uncertain workload. In this paper, we propose and analyze a feedback scheduling algorithm, called double-loop feedback scheduler, for distributed real-time systems, whose objective is to keep the deadline miss ratio near the desired value and achieve high CPU utilization. This objective is achieved by an integrated design of a local and a global feedback scheduler. We provide the stability analysis of the double-loop system. We also carry out extensive simulation studies to evaluate the performance and stability of the proposed double-loop scheduler. Our studies show that the proposed scheduler achieves high CPU utilization with low miss ratio and stays in steady state after a step change in workload, characterized by change in actual execution time of tasks.