Energy-E cient Low-latency Audio on Android

Counting more than two billion devices, Android is nowadays one of the most popular open-source general-purpose operating systems, based on Linux. Because of the diversity of applications that can be installed, it manages a number of di erent workloads, many of them requiring performance/QoS guarantees. When running audio processing applications, the user would like an uninterrupted, glitch-free, output stream that reacts to the user input, typically with a delay not bigger than 4− 10 ms, while keeping the energy consumption of the mobile device as low as possible. This work focuses on improvements to the real-time audio processing performance on Android that preserves energy-e ciency. Such improvements are achieved by using a deadline based scheduler and an adaptive scheduling strategy that dynamically and proactively modulates the allocated runtime. The proposed strategy is evaluated through an extensive experimentation, showing that 1) compared to the existing way to ensure low-latency audio processing, the proposed mechanism provides an energy saving of almost 40%, and 2) compared to the existing way to achieve a good balance between power consumption and latency in a glitch-free audio processing experience, the proposed solution reduces audio latency from 26.67 ms to 2.67 ms, at the expense of a limited Email addresses: alessio.balsini@santannapisa.it (Alessio Balsini), tommaso.cucinotta@santannapisa.it (Tommaso Cucinotta), luca.abeni@santannapisa.it (Luca Abeni), joelaf@google.com (Joel Fernandes), philburk@google.com (Phil Burk), patrick.bellasi@arm.com (Patrick Bellasi), morten.rasmussen@arm.com (Morten Rasmussen) Preprint submitted to Journal of Systems and Software March 10, 2019 power consumption increase of 6.25%.