CAPMAN: Cooling and Active Power Management in big.LITTLE Battery Supported Devices

EasyChair Preprint no. 3215

Abstract

Modern smartphone is far from being ubiquitous due to limited energy capacity. %Equipping larger battery may mitigate such deficiency/defects %yet it raises challenges on thermal limit and physical size. Recent research suggests that heterogeneous batteries may expose power saving opportunities that fit dynamic software patterns. % in mobile device domain. Yet it is still a challenge on thermal and power management for a hybrid battery pack in a smartphone. To address this challenge, we propose a system framework, called \Sysname, which supports joint optimization of \underline{\emph{c}}ooling and \underline{\emph{a}}ctive \underline{\emph{p}}ower \underline{\emph{man}}agement in smartphones. The framework consists of three major techniques: 1) A Markov decision process (MDP) technique that models battery types, and cooling/active power use from state and action nodes; 2) A structural similarity approximation that speeds up the convergence of MDP computation, providing battery scheduling decisions; 3) A TEC and battery management facility to realize the cooling and active power management. In addition, CAPMAN provides an online algorithm with a proved worst-case O($\dfrac{1}{1-\rho}$)-competitiveness performance.%O(1+$\dfrac{\rho}{1-\rho}$) We have prototyped \Sysname with popular smartphones and heterogeneous batteries, and evaluated them with real-world workloads. Results show that \Sysname can achieve 114\% longer service time under skewed loads, compared to the original phone. Compared to the state-of-the-practice baselines, \Sysname shows 55\% performance gain and 53\% less energy use on average. As such, \Sysname approves that big.LITTLE batteries with a careful system design is an effective way to prolong smartphone service times.

Keyphrases: Battery scheduling, MDP-based approximation, power/performance evaluation, software-defined battery

@Booklet{EasyChair:3215,
  author = {Jie Zhou and Zichen Xu and Wenli Zheng and Yuhao Wang},
  title = {CAPMAN: Cooling and Active Power Management in big.LITTLE Battery Supported Devices},
  howpublished = {EasyChair Preprint no. 3215},

  year = {EasyChair, 2020}}