The document proposes adding instrumentation to the Android emulator to capture hardware events and metrics like duty cycle and clock frequency. This would allow using existing power models to estimate the energy consumption of apps as if they were running on real devices. The project would involve modifying the Android emulator to log low-level information and building a Python energy profiling tool that implements power models for components like the modem, GPS, screen, WiFi and CPU. It provides details on the Android emulator architecture and describes code for modeling the states and power consumption of the modem component as a proof of concept.

1. Energy Profiler for Android Emulator
Diego Ruggeri
diego@ruggeri.net.br

2. Project Proposal Energy-Aware Computing 2
Project Outline
Energy Profiler for Android Emulator
• Project Summary
• Android Emulator
• Energy Model Archtecture
• Code
• Demo

3. Project Proposal Energy-Aware Computing 3
Project Summary
• Add instrumentation to Android Emulator to capture hardware events, duty
cycle, clock frequency, etc.
• Use existing power models to predict consumption in real devices
• Empowering Developers to Estimate App Energy Consumption
• Modem state machine

4. Project Proposal Energy-Aware Computing 4
Android Emulator
• Two versions of android emulator
• The first is a fork of qemu, incompatible with the mainline (repo qemu)
It emulates a hardware called goldfish, which has an specific android
kernel for it.
• The newer one was started by linaro to support arm v8 64 bits using
qemu 2.0 source code and is now default (repo qemu-android)
The emulated hardware is called ranchu
It is periodically rebased on top of latest qemu
• Tracetool generates tracing glue code for multiple backends
A file trace-events specify events end formats

5. Project Proposal Energy-Aware Computing 5
Android Emulator
• To build you need to use repo tool to download multiple gits
• Total was about 8 GB of code, 11 GB after building
• I used the studio-dev branch
• Then switched to the most up-to-date is emu-master-dev
• qemu, android-qemu
• dependencies, libs
• sdk, ndk
• cross-compilers: gcc (linux), clang (mac), mingw (windows)
• 32 and 64 bits
• kernel

6. Project Proposal Energy-Aware Computing 6
Android Emulator
https://github.com/android-energy/platform_external_qemu/blob/emu-
master-dev/docs/ANDROID-EMULATION-LIBRARY.TXT

7. Project Proposal Energy-Aware Computing 7
Energy Model Archtecture
- Modem
- GPS
- Screen
- Wifi
- CPU

8. Project Proposal Energy-Aware Computing 8
Energy Model Archtecture
• Python Implementation
• Invoke an modified emulator which print logs on stderr
• Each component can register to be notified if some tag appear on the log
• Each component run on its own thread and compute its power according to
the models
• The device model sums the power of its components
• The only compoent implemented was the modem
• Each time the driver sends a message, the modem goes to active mode
(DCH), and after some time will transition to intermediate states until it goes to
sleep again or goes back to DCH.

9. Project Proposal Energy-Aware Computing 9
Code: Modem States

10. Project Proposal Energy-Aware Computing 10
Code: State Transition

11. Project Proposal Energy-Aware Computing 11
Code: Device Model

12. Project Proposal Energy-Aware Computing 12
Demo