2x slower android builds after upgrading to 0.76

[ethanneff]

Description

Our Android builds are significantly slower after upgrading from 0.75.4 to 0.76.5

A large amount of time is doing C work because of the new architecture. Is this expected?

• 2024-12-17T09:09:48.5675575Z [09:09:48]: ▸ [35m> Task :app:buildCMakeRelWithDebInfo[arm64-v8a][0m 4 minutes
• 2024-12-17T09:14:01.6679960Z [09:14:01]: ▸ [35m> Task :app:buildCMakeRelWithDebInfo[armeabi-v7a][0m 2 minutes
• 2024-12-17T09:17:40.9667954Z [09:17:40]: ▸ �[35m> Task :app:configureCMakeRelWithDebInfo[x86]�[0m 30 seconds
• 2024-12-17T09:18:10.8667528Z [09:18:10]: ▸ [35m> Task :app:buildCMakeRelWithDebInfo[x86][0m 2 minutesa

Steps to reproduce

1. run ./gradlew assembleRelease assembleDebug on a react native without framework
2. compare 0.75.4 speeds to 0.76.5 speeds

React Native Version

0.76.5

Affected Platforms

Runtime - Android

Areas

JSI - Javascript Interface, Codegen

Output of npx react-native info

❯ npx react-native info
info Fetching system and libraries information...
System:
  OS: macOS 15.1.1
  CPU: (12) arm64 Apple M3 Pro
  Memory: 279.53 MB / 36.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 20.12.0
    path: ~/.nvm/versions/node/v20.12.0/bin/node
  Yarn:
    version: 1.22.22
    path: ~/.nvm/versions/node/v20.12.0/bin/yarn
  npm:
    version: 10.8.2
    path: ~/Documents/adaptedmind/AdaptedMindMobile/node_modules/.bin/npm
  Watchman:
    version: 2024.09.23.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.15.2
    path: /opt/homebrew/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.1
      - iOS 18.1
      - macOS 15.1
      - tvOS 18.1
      - visionOS 2.1
      - watchOS 11.1
  Android SDK:
    API Levels:
      - "33"
      - "34"
      - "35"
    Build Tools:
      - 30.0.3
      - 33.0.0
      - 33.0.1
      - 34.0.0
      - 35.0.0
      - 35.0.0
    System Images:
      - android-30 | Google Play ARM 64 v8a
      - android-34 | Google APIs ARM 64 v8a
      - android-34 | Google APIs Intel x86_64 Atom
      - android-34 | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2024.2 AI-242.23339.11.2421.12700392
  Xcode:
    version: 16.1/16B40
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.12
    path: /usr/bin/javac
  Ruby:
    version: 3.3.1
    path: /Users/eneff/.rvm/rubies/ruby-3.3.1/bin/ruby
npmPackages:
  "@react-native-community/cli": Not Found
  react: Not Found
  react-native: Not Found
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

### Stacktrace or Logs


before

https://gist.github.com/ethanneff/581ae74c327fe18f65c792d622a08640

after

https://gist.github.com/ethanneff/2eb0b8e8196f209834e147b5f0c95ed3

### Reproducer

https://github.com/facebook/react-native

### Screenshots and Videos

attached

[react-native-bot]

Warning

Missing reproducer: We could not detect a reproducible example in your issue report. Please provide either:

• If your bug is UI related: a Snack
• If your bug is build/upgrade related: a project using our Reproducer Template
• Otherwise send us a Pull Request with the RNTesterPlayground.js edited to reproduce your bug.

[cipolleschi]

@ethanneff Yes, this is expected. The New Architecture is written in C++ a lot of the code is written with that language.

That's also why we ship prebuilds for React Native on Android. Regular apps does not have to rebuild React Native for Android and the build time is in the order or a few minutes.

I assume that you are building React Native from source. Can I ask you why? Why do you have to maintain a fork of React Native instead of consuming the prebuilds?

[lovegaoshi]

I personally see a 30% increase in build time on android (20min old arch vs 27min new) the only difference is simply newarch=true.

My previous experience building rn from source with the default github actions runners takes ~1h.

[cipolleschi]

@lovegaoshi I'm not that big of an expert of Android build system, we should wait for @cortinico to be back. However, it would help if you can share your gradle logs to understand where the build is taking more time.

In theory, if you don't have custom C++ code and you are consuming prebuilds from react native, the build time should not increase that much.

[cortinico]

@ethanneff Yes, this is expected. The New Architecture is written in C++ a lot of the code is written with that language.

As @cipolleschi mentioned, the New Architecture relies on C++ for component/module registration, so there is another compiler to run, link, etc. So yes is expected that building could be a bit slower than Old Arch.

However I see from your build log that you're building all the Native Architectures: armeabi-v7a,arm64-v8a,x86,x86_64.

The suggestion is to build only the architecture you need (generally arm64-v8a is sufficient), and build all of them only once you need to publish to a store.

You can also consider using caching (such as ccache or the setup-gradle GitHub Action to speed up your build step) on CI.

You can read more about it here: https://reactnative.dev/docs/next/build-speed