High memory usage for `Text` component on iOS
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描述
Description
When working on memory optimisation of a complex RN app, I found that Text components on iOS can consume relatively large amounts of memory. When I've checked that with Xcode Instruments, it seems that each RCTParagraphTextView is accompanied by a backing CALayer which consumes memory proportional to its rendered size, more precisely width x height x 4 bytes (RGBA channels).
While individual Text instances are small, complex UI, esp. using stacked screens & virtualized lists can add up to quite large number (tens of MB), especially if the app uses large font sizes in such lists.
For example, each of the following Text components consumes about 112-140 KB of memory, due to the backing raster.
This can be observed using Allocations Xcode Instrument by marking memory before and after adding text views.
I've created a small app for easily measuring various components' memory usage: https://github.com/mdjastrzebski/rn-memory-footprint
Note:
- on Android, this issue does not seem to happen, as all Text have similar size, regardless of used font size
- on iOS, when using native
UILabel, these are much smaller, and do not haveCALayersattached
Steps to reproduce
- Download the reproducer app
yarn install&yarn ios:releaseORyarn android:release- Run the app on a simulator or a device
- Attach Allocation Xcode Instrument, mark generation A
- Pick "Text (Large Font)" from the component dropdown
- Press "Create Views"
- Wait a couple of seconds, mark generation B in instruments
- Compare memory usage. You should see a lot of
RCTParagraphTextView (CALayer)entries, each taking 120-140 KBs.
React Native Version
0.82.1
Affected Platforms
Runtime - iOS
Output of npx @react-native-community/cli info
System:
OS: macOS 26.1
CPU: (11) arm64 Apple M3 Pro
Memory: 102.75 MB / 36.00 GB
Shell:
version: "5.9"
path: /bin/zsh
Binaries:
Node:
version: 22.17.1
path: /Users/mdj/.nvm/versions/node/v22.17.1/bin/node
Yarn:
version: 4.12.0
path: /Users/mdj/.nvm/versions/node/v22.17.1/bin/yarn
npm:
version: 10.9.2
path: /Users/mdj/.nvm/versions/node/v22.17.1/bin/npm
Watchman:
version: 2025.07.28.00
path: /opt/homebrew/bin/watchman
Managers:
CocoaPods:
version: 1.16.2
path: /Users/mdj/.rbenv/shims/pod
SDKs:
iOS SDK:
Platforms:
- DriverKit 25.0
- iOS 26.0
- macOS 26.0
- tvOS 26.0
- visionOS 26.0
- watchOS 26.0
Android SDK:
API Levels:
- "35"
- "36"
Build Tools:
- 35.0.0
- 36.0.0
System Images:
- android-35 | Google Play ARM 64 v8a
- android-36 | Google Play ARM 64 v8a
Android NDK: Not Found
IDEs:
Android Studio: 2025.2 AI-252.25557.131.2521.14432022
Xcode:
version: 26.0.1/17A400
path: /usr/bin/xcodebuild
Languages:
Java:
version: 17.0.16
path: /usr/bin/javac
Ruby:
version: 3.4.5
path: /Users/mdj/.rbenv/shims/ruby
npmPackages:
"@react-native-community/cli":
installed: 20.0.0
wanted: 20.0.0
react:
installed: 19.1.1
wanted: 19.1.1
react-native:
installed: 0.82.1
wanted: 0.82.1
react-native-macos: Not Found
npmGlobalPackages:
"*react-native*": Not Found
Android:
hermesEnabled: true
newArchEnabled: true
iOS:
hermesEnabled: true
newArchEnabled: true
Stacktrace or Logs
n/a
MANDATORY Reproducer
https://github.com/mdjastrzebski/rn-memory-footprint
Screenshots and Videos
Added above
贡献指南
从这里开始
- 先读完整个 Issue,再读项目的贡献指南。
- 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
- Fork 仓库,在一个分支上完成修改。
- 提交 Pull Request,并在描述里引用这个 Issue 编号。
调研方向
使用“Text (Large Font)”组件和 Xcode Allocations Instrument,通过链接的 rn-memory-footprint 应用复现该问题。首先跟踪 RCTParagraphTextView 及其底层 CALayer,然后将观察到的 iOS 行为与原生 UILabel 和 Android 进行比较;在不改变 Text 行为的情况下解决每个视图过高的内存使用量,即表示完成。
由索引模型根据 Issue 内容生成。
评估
- 技术栈
- ios, react-native
- 领域
- mobile, performance
- Issue 类型
- 缺陷
- 难度
- 4/5
- 预计耗时
- 3-5 天
- 活跃度
- 冷清
- 描述清晰度
- 基本清楚
- 新手友好度
- 45/100