Macrobenchmarks

Performance benchmarks use either flutter drive or the web benchmark harness.

Mobile benchmarks

Cull opacity benchmark

To run the cull opacity benchmark on a device:

flutter drive --profile test_driver/cull_opacity_perf.dart

Results should be in the file build/cull_opacity_perf.timeline_summary.json.

More detailed logs should be in build/cull_opacity_perf.timeline.json.

Cubic bezier benchmark

To run the cubic-bezier benchmark on a device:

flutter drive --profile test_driver/cubic_bezier_perf.dart

Results should be in the file build/cubic_bezier_perf.timeline_summary.json.

More detailed logs should be in build/cubic_bezier_perf.timeline.json.

Backdrop filter benchmark

To run the backdrop filter benchmark on a device: To run a mobile benchmark on a device:

flutter drive --profile -t test_driver/run_app.dart --driver test_driver/[test_name]_test.dart

Results should be in the file build/[test_name].timeline_summary.json.

More detailed logs should be in build/[test_name].timeline.json.

The key [test_name] can be:

• animated_placeholder_perf
• backdrop_filter_perf
• cull_opacity_perf
• fading_child_animation_perf
• imagefiltered_transform_animation_perf
• multi_widget_construction_perf
• picture_cache_perf
• post_backdrop_filter_perf
• simple_animation_perf
• textfield_perf
• cubic_bezier_perf

Web benchmarks

Web benchmarks are compiled from the same entry point in lib/web_benchmarks.dart.

How to write a web benchmark

Create a new file for your benchmark under lib/src/web. See bench_draw_rect.dart as an example.

Choose one of the two benchmark types:

• A "raw benchmark" records performance metrics from direct interactions with dart:ui with no framework. This kind of benchmark is good for benchmarking low-level engine primitives, such as layer, picture, and semantics performance.
• A "widget benchmark" records performance metrics using a widget. This kind of benchmark is good for measuring the performance of widgets, often together with engine work that widget-under-test incurs.
• A "widget build benchmark" records the cost of building a widget from nothing. This is different from the "widget benchmark" because typically the latter only performs incremental UI updates, such as an animation. In contrast, this benchmark pumps an empty frame to clear all previously built widgets and rebuilds them from scratch.

For a raw benchmark extend RawRecorder (tip: you can start by copying bench_draw_rect.dart).

For a widget benchmark extend WidgetRecorder (tip: you can start by copying bench_simple_lazy_text_scroll.dart).

For a widget build benchmark extend WidgetBuildRecorder (tip: you can start by copying bench_build_material_checkbox.dart).

Pick a unique benchmark name and class name and add it to the benchmarks list in lib/web_benchmarks.dart.

How to run a web benchmark

Web benchmarks can be run using flutter run in debug, profile, and release modes, using either the HTML or the CanvasKit rendering backend. Note, however, that running in debug mode will result in worse numbers. Profile mode is useful for profiling in Chrome DevTools because the numbers are close to release mode and the profile contains unobfuscated names.

Example:

cd dev/benchmarks/macrobenchmarks

# Runs in profile mode using the HTML renderer
flutter run --profile -d web-server lib/web_benchmarks.dart

# Runs in profile mode using the CanvasKit renderer
flutter run --dart-define=FLUTTER_WEB_USE_SKIA=true --profile -d web-server lib/web_benchmarks.dart

You can also run all benchmarks exactly as the devicelab runs them:

cd dev/devicelab

# Runs using the HTML renderer
../../bin/cache/dart-sdk/bin/dart bin/run.dart -t bin/tasks/web_benchmarks_html.dart

# Runs using the CanvasKit renderer
../../bin/cache/dart-sdk/bin/dart bin/run.dart -t bin/tasks/web_benchmarks_canvaskit.dart