# `mix dala.battery_bench_android`
[🔗](https://github.com/manhvu/dala_dev/blob/main/lib/mix/tasks/dala.battery_bench_android.ex#L1)

Builds a benchmark APK, deploys it, and measures battery drain over time.

Run this from your Dala app project directory (the one containing `android/`,
`dala.exs`, and your Elixir source). It requires `bundle_id` to be set in
`dala.exs`:

    config :dala_dev,
      dala_dir:   "/path/to/dala",
      bundle_id: "com.example.myapp"

Reports mAh every 10 seconds and prints a summary at the end.
WiFi ADB is required for accurate measurements (USB cable charges the battery).

## Setup (one-time, while plugged in)

    adb -s SERIAL tcpip 5555
    adb connect PHONE_IP:5555
    # then unplug and pass PHONE_IP:5555 as --device

## Recommended workflow

Same two-step pattern as iOS — push BEAM flags via `mix dala.deploy`, then
bench with `--no-build`. Lets you change tuning without a Gradle rebuild.

    # 1. Push BEAM flags via dala.deploy (no APK rebuild — ~10 sec).
    mix dala.deploy --beam-flags "" --android              # tuned (Nerves)
    mix dala.deploy --beam-flags "-S 4:4 -A 8" --android   # untuned variant

    # 2. Run the bench with --no-build.
    mix dala.battery_bench_android --no-build --device 192.168.1.42:5555

See `README.md` for the full rationale and recovery procedure.

## Usage (with built-in Gradle build path)

    mix dala.battery_bench_android
    mix dala.battery_bench_android --no-beam
    mix dala.battery_bench_android --preset nerves
    mix dala.battery_bench_android --flags "-sbwt none -S 1:1"
    mix dala.battery_bench_android --duration 3600 --device 192.168.1.42:5555
    mix dala.battery_bench_android --no-build   # re-run without rebuilding

## Options

  * `--duration N`      — benchmark duration in **seconds** (default: 1800 = 30 min)
  * `--device SERIAL`   — adb device serial or IP:port (auto-detected if omitted)
  * `--no-beam`         — baseline: build without starting the BEAM at all
  * `--no-keep-alive`   — skip the foreground-service background keep-alive call
  * `--preset NAME`     — named BEAM flag preset (Gradle-build path only)
  * `--flags "..."`     — arbitrary BEAM VM flags (Gradle-build path only)
  * `--no-build`        — skip APK build and install; run benchmark on current install
  * `--log-path PATH`   — override CSV log location (default: `_build/bench/run_android_<ts>.csv`)
  * `--no-csv`          — skip CSV logging
  * `--skip-preflight`  — bypass the preflight checks (adb/app/BEAM/RPC/NIF/keep-alive)

## What the presets do

  * `untuned`   — raw BEAM with no tuning flags (highest power use baseline)
  * `sbwt`      — only busy-wait disabled (`-sbwt none`)
  * `nerves`    — full Nerves set: single scheduler + busy-wait off + multi_time_warp
  * (default)   — same as `nerves` (production default)

## Understanding the results

The BEAM with Nerves-style tuning flags uses roughly the same power as an app
with no BEAM at all (~200 mAh/hr on a Moto G, 30-min run). The untuned BEAM
uses ~25% more power due to scheduler busy-waiting. For most apps the overhead
is in the noise; tune if you have stricter power budgets.

## Under the hood

`mix dala.battery_bench_android` orchestrates the following adb and Gradle commands:

    # Build and install
    ./gradlew assembleDebug [-PextraCppFlags="-DNO_BEAM|..."]
    adb install -r app/build/outputs/apk/debug/app-debug.apk

    # Push BEAMs
    adb push _build/dev/lib/*/ebin/*.beam /data/data/<pkg>/files/otp/<app>/

    # Reset battery stats and launch
    adb shell dumpsys batterystats --reset
    adb shell am start -n <pkg>/.MainActivity

    # Turn screen off
    adb shell input keyevent 26          # KEYCODE_POWER

    # Poll battery every 10s
    adb shell dumpsys battery            # reads "Charge counter: <µAh>"

    # Stop app and collect final reading
    adb shell am force-stop <pkg>
    adb shell dumpsys battery

BEAM tuning flags are injected as C preprocessor defines (`-DBEAM_UNTUNED`,
  `-DBEAM_FULL_NERVES`, etc.) or via a generated `dala_beam_flags.h` header, so
  each preset compiles a different variant of the BEAM startup C code.

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*Consult [api-reference.md](api-reference.md) for complete listing*