Binary Size Metrics

This document lists metrics used to track binary size.

[TOC]

Metrics for Desktop

For Googlers, more information available at go/chrome-apk-size.

Sizes are collected by //build/android/resource_sizes.py.
How to analyze Android binary size discussed in apk_size_regressions.md#debugging-apk-size-increase.
Sizes for ChromePublic.apk, ChromeModernPublic.apk, TrichromeChrome.aab, SystemWebview.apk are tracked.
- But only TrichromeChrome.aab is actively monitored.
We care most about on-disk size (for users with small device storage)
- But also care about patch size (so that browser updates get applied)

Telemetry Graph
Monitored by Binary Size Sheriffs.
- Alerts fire for changes of 16kb or more.
Computed as:
- The size of an APK
- With all native code as the sum of section sizes (except .bss), uncompressed.
  - Why: Removes effects of ELF section alignment.
- With all dex code as if it were stored uncompressed.
  - Why: Best practice is to store dex uncompressed on Android P and above.
  - On prior versions, or when stored compressed, dex is extracted upon installation.
- With all zipalign padding removed.
  - Why: Removes effects of file alignment (esp. relevant because native libraries are 4k-aligned).
- With size of apk signature block removed.
  - Why: Size fluctuates by several KB based on how hash values turn out.
- With all translations as if they were not missing (estimates size of missing translations based on size of english strings).
  - Why: Without translation-normalization, translation dumps cause jumps.
  - Translation-normalization applies only to apks (not to Android App Bundles).
For Android App Bundles, the normalized size is the sum of the normalized size of all splits that have onDemand="false" (those installed by default).

Telemetry Graph
File size of classes.dex
"Dex": Counts of the number of fields, methods, strings, types.
"DexCache": The number of bytes of RAM required to load our dex file (computed from counts)

Telemetry Graph
Compressed size of each apk component.
The sum of these equals APK Size (which can be found under "Install Size Metrics": "APK Size")

Telemetry Graph
Estimated installed size: How much disk is required to install Chrome on a device.
- This is just an estimate, since actual size depends on Android version (e.g. Dex overhead is very different for pre-L vs L+).
- Does not include disk used up by profile, etc.
- We believe it to be fairly accurate for all L+ devices (less space is required for Dalvik runtime pre-L).
The sum of these equals Estimated installed size.

Deflated apk size:
- Telemetry Graph
- Only relevant for non-patch updates of Chrome (new installs, or manual app updates)
Patch Size (no longer available):
- Is too slow to be running on the Perf Builder
- Was found to be fairly unactionable
- Used to use https://github.com/googlesamples/apk-patch-size-estimator
- Functionality now exists in //third_party/android_sdk/public/cmdline-tools/latest/bin/apkanalyzer download-size