Fixed priority scheduling for reducing overall energy on variable voltage processors

While dynamic voltage scaling (DVS) is an efficient technique in reducing the dynamic energy consumption of a CMOS processor, methods that employ DVS without considering leakage current are quickly becoming less efficient when considering the processor´s overall energy consumption. A leakage conscious DVS voltage schedule may require the processor to run at a higher-than-necessary speed to execute a given set of real-time tasks, which can result in a large number of idle intervals. To effectively reduce the energy consumption during these idle intervals, and therefore the overall energy consumption, the DVS schedule must judiciously allow the processor to enter and leave the power down state during these idle intervals, while considering the time and energy cost of doing so. In this paper, we present a scheduling technique that can effectively reduce the overall energy consumption for hard real-time systems scheduled according to a fixed priority (FP) scheme. Experimental results demonstrate that a processor using our strategy consumes as less as 15% of the idle energy of a processor employing the conventional strategy.