EnTrack: A System Facility for Analyzing Energy Consumption of Android System Services

Background Energy efficiency is a critical issue for mobile device. Energy accounting is essential for developing energy-efficient applications. Previous studies consider the energy consumption of an application as the summation of the energy consumption of the constituent processes(the processes and threads with the same UID). Such energy consumption methods are not accurate when considering system service!

Energy Models 22.2% of energy consumption is attributed to System Processes

Innovations Tracking the relationship between applications and services Providing fine-grained energy consumption of system services according to function unit Accounting the energy consumption of applications linked with system services.

EnTrack Architecture

Service Tracer Binder Tracer Interaction Identifier Hook into Binder Driver [jprobe] Acquire IPC message Interaction Identifier Analyze data from Binder Tracer Interaction Data Manager Maintain a caller list of system service Framework Tracer Deal with location & graphics processing

Framework Tracer

HW Usage Accounter & Application Energy Analyzer Hardware Usage Accounter Collect hardware usage information The same way as AppScope Application Energy Analyzer Process-level energy consumption CPU and network energy consumption The same as AppScope Disaggregate energy consumption of system service to the caller Decompose energy consumption at GPU according to the display proportion Decompose energy consumption at GPS equally to applications which use GPS concurrently

Evaluation: Accuracy & Functionality Service Tracker Hardware Usage Accounter Add code to log service usage information Execute five applications both sequentially and simultaneously. Rerun the scenario and collect data with EnTrack A margin of error of 4.94% Compare the monitoring results: exactly the same

Evaluation: Accuracy & Functionality Application Energy Analyser

Evaluation Analysis Capability Overhead CPU Utilization: 1.8% Memory Overhead: Rather High Log size of 450-second scenario: 581 KB

Case Study 1: LBS Application Two versions of a LBS application: Old version: use AlarmManager to activate GPS sensor and it consumes most energy. New version: use Handler instead of AlarmManager to activate GPS sensor.

Case Study 2: Web Browser Optimization Tab Switching Optimization: Overall energy usage decreased from 90,000mJ to 65,800mJ Version 25.0: Load the images in all web pages Version 26.0: Only load images visible to the user

Case Study 3: Energy Bug of Web Browser Firefox continues to operate the timer or video when the application runs in the background. EnTrack tracks the energy consumption with the android.hardware.IOMX system service in the Media Server. android.hardware.IOMX continuously consumes a certain amount of energy although the application does not consume energy for display.

Conclusion EnTrack keeps track of interactions between application and system service and disaggregates energy consumption of system services to each application. Evaluation shows that EnTrack improves analysis capability of energy consumption compared with the existing method. The case studies show that EnTrack can be used as a developer tool for energy optimization. The limitation of EnTrack is that the energy consumption used by the kernel is not considered.