Low Power Round-Robin Scheduling
Abstract
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. The processor being an important 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 Round-Robin 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 reduces 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.