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Summary: Okay the title is a bit clickbaity, but this is actually true. (on Android) We (Janic, Szymon, Ruby and Me) discovered something interesting. React Native uses `mmap` for mapping the JS bundle to RAM, to avoid having to load the entire thing instantly at app startup. Ruby doubted that this was true - so we investigated. Apparently on Android, resources are **compressed**. And if the JS bundle is stored compressed, it has to be uncompressed before it can be loaded into RAM, hence not allowing it to be mmapp'ed! (see [`_CompressedAsset::getBuffer`](https://cs.android.com/android/platform/superproject/+/master:frameworks/base/libs/androidfw/Asset.cpp;l=903?q=Asset.cpp)) So with this PR, we now add `.bundle` files to `noCompress` in the react-native gradle plugin, which disables compression for the JS bundle. We discovered while improving the performance of one of our clients: **Discord**. In our tests, **this improved the TTI of the Discord app by 400ms!! (or 12%)** 🤯🚀 NOTE: Yes, the .apk will now be bigger. But; Google Play compresses it anyways, so the **download size** of your .apk will likely not increase by much. It will be bigger on disk though. ## Changelog: [ANDROID] [CHANGED] Add option to disable bundle compression to improve startup time <!-- Help reviewers and the release process by writing your own changelog entry. Pick one each for the category and type tags: [ANDROID|GENERAL|IOS|INTERNAL] [BREAKING|ADDED|CHANGED|DEPRECATED|REMOVED|FIXED|SECURITY] - Message For more details, see: https://reactnative.dev/contributing/changelogs-in-pull-requests Pull Request resolved: https://github.com/facebook/react-native/pull/49449 Test Plan: ### 1. Verify compression is disabled Build two apps, one with this patch and one without. When I did this using the RN community template, the one without this patch was 47,6 MB, and the one with this patch was 48 MB in size. So the .apk got bigger, which is what we expected ### 2. Verify app startup is faster Use tools like react-native-performance or custom markers to measure TTI. In our tests, we shaved off 400ms from the startup time, which was about 12% of Discord's total TTI. (on a low-end Android device) In Expensify, we improved the TTI by 14-20% with this change (source: https://github.com/Expensify/App/pull/56930) Reviewed By: javache, cipolleschi Differential Revision: D69742221 Pulled By: cortinico fbshipit-source-id: bd59d77662bd30a3acdbb2e9f8d8f23db922c3f2
@react-native/gradle-plugin
A Gradle Plugin used to support development of React Native applications for Android.
Installation
yarn add @react-native/gradle-plugin
Note: We're using yarn to install deps. Feel free to change commands to use npm 3+ and npx if you like
Testing
To run the tests in this package, run the following commands from the React Native root folder:
yarnto install the dependencies. You just need to run this once./gradlew -p packages/gradle-plugin test.