A Control-Theoretic Energy Management for Fault-Tolerant Hard Real-Time Systems

Recently, the tradeoff between low energy consumption and high fault-tolerance has attracted a lot of attention as a key issue in the design of real-time embedded systems. Dynamic Voltage Scaling (DVS) is known as one of the most effective low energy techniques for real-time systems. It has been observed that the use of control-theoretic methods can improve the effectiveness of DVS-enabled systems. In this paper, we have investigated reducing the energy consumption of fault-tolerant hard real-time systems using feedback control theory. Our proposed feedback-based DVS method makes the system capable of selecting the proper frequency and voltage settings in order to reduce the energy consumption while guaranteeing hard real-time requirements in the presence of unpredictable workload fluctuations and faults. In the proposed method, the available slack-time is exploited by a feedback-based DVS at runtime to reduce the energy consumption. Furthermore, some slack-time is reserved for re-execution in case of faults. Simulation results show that, as compared with traditional DVS methods without fault-tolerance, our proposed approach not only significantly reduces energy consumption, but also it satisfies hard real-time constraints in the presence of faults. The transition overhead (both time and energy), caused by changing the system supply voltage, are also taken into account in our simulation experiments. (Abstract)