BrezeFlow: Unified Debugger for Android CPU Power Governors and Schedulers on Edge Devices

Abstract

Power management is quintessential to the successful deployment of edge devices, such as smartphones, in power-, thermal-, and energy-constrained environments. Governors and schedulers operate system sub-routines for power management at the edge. There exist several tools for debugging power issues in Android applications. However, there exists no tool to identify and classify inevitable misdecisions by power managers, given their often inefficient underlying heuristics. In this work, we introduce the first tool - BrezeFlow - designed for unified (scheduling and frequency scaling) power debugging of CPU power managers on Android edge devices. BrezeFlow enables kernel developers to evaluate designs of their power managers retrospectively with closed-source applications in real-world scenarios based on any user-defined strategy and thereby gain insights for better future governor designs. BrezeFlow detected an average of 815 misdecisions per second for the commonly deployed duo, ondemand governor and Completely Fair Scheduler, on mobile edge devices running popular applications.