diff --git a/runtime/docs/timeline-complete.webp b/runtime/docs/timeline-complete.webp new file mode 100644 index 00000000000..b67205f5bef Binary files /dev/null and b/runtime/docs/timeline-complete.webp differ diff --git a/runtime/docs/timeline-file.webp b/runtime/docs/timeline-file.webp new file mode 100644 index 00000000000..68fa0442cb2 Binary files /dev/null and b/runtime/docs/timeline-file.webp differ diff --git a/runtime/docs/timeline.md b/runtime/docs/timeline.md new file mode 100644 index 00000000000..dbab9706e36 --- /dev/null +++ b/runtime/docs/timeline.md @@ -0,0 +1,67 @@ +# Timeline + +The timeline, also called tracing, provides a way to see when manually annotated events are running and how much time they are taking. + +## Recorders + +| Name | Description | +| --------- | ------------| +| `none` | All events are dropped. | +| `ring` | Fixed-size buffer. Once full, new events overwrite the oldest events. | +| `startup` | Fixed-size buffer. Once full, new events are dropped. | +| `endless` | Infinite buffer. Eventually the process may die from hitting out of memory. | +| `file` | Writes events to a file in [Chrome Trace Format](https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU). This format can be visualized with `chrome://tracing`. | +| `systrace` (Linux/Android) | Writes events to [Systrace](https://source.android.com/docs/core/tests/debug/systrace). | +| `systrace` (Fuchsia) | Writes events to [Fuchsia tracing](https://fuchsia.dev/fuchsia-src/development/tracing/). | +| `systrace` (Mac/iOS) | Writes events to [Signposts](https://help.apple.com/instruments). | + +The recorder can be selected with the `timeline_recorder` flag. E.g., `--timeline_recorder=startup` or `--timeline_recorder=file=mytrace.json`. + +If the recorder uses a VM-internal buffer (`ring`, `startup`, `endless`), then the timeline can be retrieved using the `getVMTimeline` method of the [VM service](../vm/service/service.md). + +## Streams + +Streams, also called categories, are sets of events whose recordering can be enabled or disabled. + +| Name | Description | +| --------- | ------------| +| `API` | Calls to the `Dart_*` embedding API functions. | +| `Compiler` | Time spent compiling Dart / RegExp to machine code. | +| `CompilerVerbose` | Events for detailed compiler phases. | +| `Dart` | Events created by `dart:developer`'s `Timeline` etc. | +| `Debugger` | | +| `Embedder` | Events created by `Dart_TimelineEvent`. | +| `GC` | Events related to garbage collection or heap iteration. | +| `Isolate` | Isolate or isolate group lifecycle events such as startup or shutdown. | +| `VM` | VM lifecycle events such a startup or shutdown. | + +The set of enabled streams can be selected with the `timeline_streams` flag. E.g., `--timeline_stream=VM,Isolate,GC,Dart` or `--timeline_streams=All`. + +The set of enabled streams can also be changed at runtime using the `setVMTimelineFlags` method of the [VM service](../vm/service/service.md). + +## Usage + +There are also some convenience flags: + +| Flag | Expansion | +| ---- | --------- | +|`--timeline_streams=All` | `--timeline_streams=API,Compiler,CompilerVerbose,Dart,Debugger,Embedder,GC,Isolate,VM` | +| `--complete_timeline` | `--timeline_recorder=endless --timeline_streams=All` | +| `--startup_timeline` | `--timeline_recorder=startup --timeline_streams=All` | + +### Example + +``` +$ dart --observe --complete-timeline hello.dart +The Dart VM service is listening on http://127.0.0.1:8181/U9AvIH-PxG8=/ +# Navigate to the URL, and select "view timeline". +``` +![Visualization of complete timeline](timeline-complete.webp) + +### Example + +``` +$ dart --timeline_recorder=file:mytimeline.json --timeline_streams=VM,Isolate,GC,Dart hello.dart +# Navigate to chrome://tracing and load mytimeline.json. +``` +![Visualization of file with select streams enabled](timeline-file.webp)