Time and Energy Efficient DVS Scheduling for Real-Time Pinwheel Tasks

Dynamic voltage/frequency scaling (DVFS) is one of the most effective techniques for reducing energy use. In thispaper, we focus on the pinwheel task model to develop a variable voltage processor with d discrete voltage/speedlevels. Depending on the granularity of execution unit to which voltage scaling is applied, DVFS scheduling can bedefined in two categories: (i) inter-task DVFS and (ii) intra-task DVFS. In the periodic pinwheel task model, wemodified the definitions of both intra- and inter-task and design their DVFS scheduling to reduce the powerconsumption of DVFS processors. Many previous approaches have solved DVFS problems by generating a canonicalschedule in advance and thus require pseudo polynomial time and space because the length of a canonical scheduledepends on the hyperperiod of the task periods and is generally of exponential length. To limit the length of thecanonical schedules and predict their task execution, tasks with arbitrary periods are first transformed into harmonicperiods and their key features are profiled. The proposed methods have polynomial time and space complexities, andexperimental results show that, under identical assumptions, the proposed methods achieve more energy savingsthan the previous methods.