Application-Specific Performance-Aware Energy Optimization on Android Mobile Devices

Energy management is a key issue for mobile devices. On current Android devices, power management relies heavily on OS modules known as governors. These modules are created for various hardware components, including the CPU, to support DVFS. They implement algorithms that attempt to balance performance and power consumption. In this paper we make the observation that the existing governors are (1) general-purpose by nature (2) focused on power reduction and (3) are not energy-optimal for many applications. We thus establish the need for an application-specific approach that could overcome these drawbacks and provide higher energy efficiency for suitable applications. We also show that existing methods manage power and performance in an independent and isolated fashion and that co-ordinated control of multiple components can save more energy. In addition, we note that on mobile devices, energy savings cannot be achieved at the expense of performance. Consequently, we propose a solution that minimizes energy consumption of specific applications while maintaining a user-specified performance target. Our solution consists of two stages: (1) offline profiling and (2) online controlling. Utilizing the offline profiling data of the target application, our control theory based online controller dynamically selects the optimal system configuration (in this paper, combination of CPU frequency and memory bandwidth) for the application, while it is running. Our energy management solution is tested on a Nexus 6 smartphone with 6 real-world applications. We achieve 4 - 31% better energy than default governors with a worst case performance loss of