PreDVS: Preemptive dynamic voltage scaling for real-time systems using approximation scheme

System optimization techniques based on dynamic voltage scaling (DVS) are widely used with the aim of reducing processor energy consumption. Inter-task DVS assigns the same voltage level to all the instances of each task. Its intra-task counterpart exploits more energy savings by assigning multiple voltage levels within each task. In this paper, we propose a voltage scaling technique, named PreDVS, which assigns voltage levels based on the task set's preemptive scheduling for hard real-time systems. Our approach is based on an approximation scheme hence can guarantee to generate solutions within a specified quality bound (e.g., within 1% of the optimal) and is different from any existing inter- or intra-task DVS techniques. PreDVS exploits static time slack at a finer granularity and achieves more energy saving than inter-task scaling without introducing any extra voltage switching overhead. Moreover, it can be efficiently employed together with existing intra-task scaling techniques. Experimental results demonstrate that PreDVS can significantly reduce energy consumption and outperform the optimal inter-task voltage scaling techniques by up to 24%.