Department of Computer Science , UTSA Technical Report : CS - TR - 2008 - 005 Reliability - Aware Energy Management for Periodic Real - Time Tasks ∗

Dynamic Voltage and Frequency Scaling (DVFS) has been widely used to manage energy in real-time embedded systems. However, it was recently shown that DVFS has direct and adverse effects on system reliability. In this work, we investigate static and dynamic reliabilityaware energy management schemes to minimize energy consumption for periodic real-time systems while preserving system reliability. Focusing on earliest deadline first (EDF) scheduling, we first show that the static version of the problem is NP-hard and propose two task-level utilization-based heuristics. Then, we develop a job-level online scheme by building on the idea of wrapper-tasks, to monitor and manage dynamic slack efficiently in reliability-aware settings. The feasibility of the dynamic scheme is formally proved. Finally, we present two integrated approaches to reclaim both static and dynamic slack at run-time. To preserve system reliability, ∗A preliminary version of this paper appeared in IEEE RTAS 2007. This work is supported in part by NSF award CNS-0720651, CNS-0720647 and NSF CAREER Award CNS-0546244.