Resource Allocation in Distributed Mixed-Criticality Cyber-Physical Systems
2010 IEEE 30th International Conference on Distributed Computing Systems
Large-scale distributed cyber-physical systems will have many sensors/actuators (each with local micro-controllers), and a distributed communication/computing backbone with multiple processors. Many cyber-physical applications will be safetycritical and in many cases unexpected workload spikes are likely to occur due to unpredictable changes in the physical environment. In the face of such overload scenarios, the desirable property in such systems is that the most critical applications continue
... to meet their deadlines. In this paper, we capture this mixedcriticality property by developing a formal overload-resilience metric called ductility. The generality of ductility enables it to evaluate any scheduling algorithm from the perspective of mixedcriticality cyber-physical systems. In distributed cyber-physical systems, this ductility is the result of both the task-to-processor packing (a.k.a bin packing) and the uniprocessor scheduling algorithms used. In this paper, we present a ductility-maximization packing algorithm to complement our previous work on mixedcriticality uniprocessor scheduling . Our packing algorithm, known as Compress-on-Overload Packing (COP) is a criticalityaware greedy bin-packing algorithm that maximizes the tolerance of high-criticality tasks to overloads. We compare the ductility of COP against the Worst-Fit Decreasing (WFD) bin-packing heuristic used traditionally for load balancing in distributed systems, and show that the performance of COP dominates WFD in the average case and can reach close to five times better ductility when resources are limited. Finally, we illustrate the practical use of COP in distributed cyber-physical systems using a radar surveillance application, and provide an overview of the entire process from assigning task criticality levels to evaluating its performance.