Combined Time and Information Redundancy for SEU-Tolerance in Energy-Efficient Real-Time Systems

Recently the trade-off between energy consumption and fault-tolerance in real-time systems has been highlighted. These works have focused on dynamic voltage scaling (DVS) to reduce dynamic energy dissipation and on time redundancy to achieve transient-fault tolerance. While the time redundancy technique exploits the available slack time to increase the fault-tolerance by performing recovery executions, DVS exploits slack time to save energy. Therefore we believe there is a resource conflict between the time-redundancy technique and DVS. The first aim of this paper is to propose the usage of information redundancy to solve this problem. We demonstrate through analytical and experimental studies that it is possible to achieve both higher transient fault-tolerance (tolerance to single event upsets (SEU)) and less energy using a combination of information and time redundancy when compared with using time redundancy alone. The second aim of this paper is to analyze the interplay of transient-fault tolerance (SEU-tolerance) and adaptive body biasing (ABB) used to reduce static leakage energy, which has not been addressed in previous studies. We show that the same technique (i.e. the combination of time and information redundancy) is applicable to ABB-enabled systems and provides more advantages than time redundancy alone

Energy and Reliability Management in Parallel Real-Time Systems

Historically, slack time in real-time systems has been used as temporal redundancy by rollback recovery schemes to increase system reliability in the presence of faults. However, with advancedtechnologies, slack time can also be used by energy management schemes to save energy. For reliable real-time systems where higher levels of reliability are as important as lower levels of energy consumption, centralized management of slack time is desired.For frame-based parallel real-time applications, energy management schemes are first explored. Although the simple static power management that evenly allocates static slack over a schedule isoptimal for uni-processor systems, it is not optimal for parallel systems due to different levels of parallelism in a schedule. Taking parallelism variations into consideration, a parallel static power management scheme is proposed. When dynamic slack is considered,assuming global scheduling strategies, slack shifting and sharing schemes as well as speculation schemes are proposed for moreenergy savings.For simultaneous management of power and reliability, checkpointing techniques are first deployed to efficiently use slack time and theoptimal numbers of checkpoints needed to minimize energy consumption or to maximize system reliability are explored. Then, an energyefficient optimistic modular redundancy scheme is addressed. Finally, a framework that encompasses energy and reliability management isproposed for obtaining optimal redundant configurations. While exploring the trade-off between energy and reliability, the effects ofvoltage scaling on fault rates are considered