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dart-sdk/runtime/docs/snapshot_profiling.md
Josh Soref 50b94ef9fc Spelling runtime bin 
TEST=build VM

Closes: https://github.com/dart-lang/sdk/pull/50862

GitOrigin-RevId: ae54b37666f70f670ee3af11c984c7e9a7e9da26
Change-Id: I459fda0439a1cd368f488a70d84ee6bb915e60bb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/277761
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
2023-01-06 07:48:22 +00:00

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AOT Snapshot Size Profiling

The VM supports profiling the size of AOT snapshots by leveraging the object-graph based file format introduced by V8.

Recording a profile

To generate a snapshot profile, simply pass the --write-v8-snapshot-profile-to=<filename> flag to gen_snapshot. The profile will be written in JSON format to the requested file. Make sure to use the ".heapsnapshot" extension for the file to open it in Chrome DevTools.

Examining a profile in Chrome

Open Chrome DevTools, navigate to the "Memory" tab, right-click on the "Profiles" panel, click Load..." and select the snapshot profile file. See https://developers.google.com/web/tools/chrome-devtools/memory-problems/heap-snapshots for details on how to use the tool.

Examining a profile programmatically

A Dart library to parse the snapshot profile format is provided in pkg/vm/lib/v8_snapshot_profile.dart. The dart2js_info package has some useful code for calculating retainers and other graph statistics.