SceneMan: Bridging mobile apps with system energy manager via scenario notification

Abstract

Power management on current mobile devices relies on OS modules known as DVFS governors. However, existing governors determine system configuration only based on low-level information such as CPU load without any input about application-level behaviors. In particular, there exists no communication from mobile apps to energy managers. We find that information about app usage scenarios (e.g., gaming, video chatting) can usually help energy manager perform a better job and achieve more energy savings. Although app-level energy optimizations have been proposed, they generally focus on single usage scenarios and do not address optimization across multiple scenarios. In this paper, we propose SceneMan, an energy optimization framework for mobile apps based on usage scenario notification. SceneMan has three components: an API, a scenario notifier, and an energy manager. The key idea is to make energy managers aware of app-level scenarios. At runtime, apps notify the energy manager about their usage scenarios with provided APIs used by developers. The energy manager then takes appropriate actions to minimize energy consumption of the running scenario while meeting performance requirements. Energy optimization across scenarios can thus be easily achieved. The framework requires little extra programming effort and can help apps achieve better energy efficiency in a transparent way. We implement our system on a Nexus 6 smartphone and test it with 13 real-world apps under 2 usage scenarios, namely, gaming and video chatting. We achieve up to 33.2% energy savings with a worst-case performance loss of 5.1%.