Flutter Performance Tuning on HarmonyOS

Flutter applications adapted for HarmonyOS can be debugged using DevTools for Dart code.

*Prerequisites*

- OpenHarmony Next system - Flutter interface running in foreground - Analysis tools: DevEco Studio Profiler SmartPerf

*Flutter Thread Architecture* Flutter utilizes multiple threads for essential operations. All Dart code executes on the UI thread, which impacts other threads:

- *Platform Thread* Main platform thread where plugin code runs - *UI Thread* Executes Dart code in Dart VM. Handles: - Developer-written code - Framework-generated code - Creates lightweight layer trees (device-agnostic rendering commands) - Sends layer trees to GPU thread *Critical:* Never block this thread! Appears in performance overlay's bottom bar. - *Raster Thread (GPU Thread)* Processes layer trees and sends to GPU. While you can't directly interact: - Slowness indicates Dart code issues - Hosts Skia graphics library - Appears in performance overlay's top bar - *I/O Thread* Handles heavy I/O operations to prevent blocking UI/raster threads. Not shown in performance overlay. - *RenderService Thread* RS process main thread. After Flutter renders frames: - Texture mode: Composites with main thread (affected by main thread) - Surface mode: Direct display (unaffected by main thread)

*Problem Boundary Definition* In DevEco Studio:

1. Open Profiler tab 2. Capture application trace 3. Focus on `<x>.ui`, `<x>.raster`, and RenderService main threads


The missing frames in the RenderService in the above image are due to the UI thread taking a longer time per frame, exceeding one frame (at a frame rate of 120, one frame is 8.33 milliseconds).


If the total duration of<x>. ui and<x>. master in a frame rendering process exceeds one frame time, the performance issue can be defined as Flutter problem. The positioning of the problem requires further performance analysis.