Low Power Round-Robin Scheduling

Energy consumption is becoming a crucial issue in the design of digital systems especially when considering portable and embedded systems due to their operational dependency on batteries. Since the processor is a major source of energy consumption, energy-aware scheduling strategies that decrease the CPU speed when possible enable to achieve significant energy savings. In this paper, we study the low-power scheduling under the RoundRobin policy which is widely available since it is part of the Posix1003.1b standard. An algorithm that computes the minimum processor speed for scheduling a job set under Round-Robin is provided. It relies on an efficient feasibility test that is also a contribution of this paper. Finally, we present mechanisms that are necessary for ensuring schedulability at run-time and that reduce consumption when jobs do not require their worst-case execution time. A counter-intuitive result shown in this study is that a job set might not be feasible at maximum frequency while being feasible with a lower frequency. This implies that even without interests in energy saving, lower frequencies have to be considered for feasibility.