Energy-Aware Dynamic Task Scheduling Applied to a Real-Time Multimedia Application on an Xscale Board

Technology advances lead to platforms with enormous processing capacity, where energy consumption is a major design issue when running real-time applications on compact and portable devices. In this paper, we focus on dynamic multimedia applications. In today's designs, worst-case implementations are used to cope with this dynamic behavior, leading to wasted resources, performance, and energy consumption. Hence a new system design methodology is needed to efficiently implement such applications on the target platform while meeting all real-time constraints, and to increase the system design productivity. Our approach addresses these challenging aspects, by combining a design-time scheduling exploration with a low-complexity run-time scheduling. This latter is integrated on top of the platform OS. In this paper, we focus on the practical aspects of our global scheduling approach and the necessary extensions. A 3D rendering application, with important load variations, and running on an Xscale processor that allows two voltages and several clock frequencies, is used as case study to demonstrate the effectiveness of our scheduling approach. For this case study, our average energy gain compared with state-of-the-art intra-task DVS is up to 40%.