These instructions can be used to prepare a tabulated summary of the differences in the sizes of two AOT snapshots. The instructions assume that the Flutter Engine has been setup on the host (at FLUTTER_ENGINE in these instructions).
Build the AOT snapshot (flutter build aot) for the application but pass in the --verbose flag. We need to find the gen_snapshot invocation and re-run it with an extra option (--print-instructions-sizes-to). If you are instrumenting with a local engine, the flutter build takes a --local-engine and --local-engine-host flag as well.
Here is an example of the updated invocation. Specify the path to a JSON file that acts as a summary (SUMMARY_LOCATION in these instructions) as follows.
$FLUTTER_ENGINE/out/host_debug_unopt/gen_snapshot \
--print-instructions-sizes-to=$SUMMARY_LOCATION \
--causal_async_stacks \
--packages=.packages \
--deterministic \
--snapshot_kind=app-aot-blobs \
--vm_snapshot_data=build/aot/vm_snapshot_data \
--isolate_snapshot_data=build/aot/isolate_snapshot_data \
--vm_snapshot_instructions=build/aot/vm_snapshot_instr \
--isolate_snapshot_instructions=build/aot/isolate_snapshot_instr \
build/aot/app.dillSave the file at SUMMARY_LOCATION as before.json
Now, either change the Dart code with the changes you wish to see the effects, or, rebuild the engine to create an updated gen_snapshot binary.
After you have made necessary changes, re-run flutter build aot again. This step is important because AOT compilation has a kernel compilation step before the gen_snapshot invocation.
Re-run the gen_snapshot invocation and save the resulting file to after.json.
Run the compare_size.dart tool and pass in the before.json and after.json files to generate the summary.
An example invocation looks as follow.
$FLUTTER_ENGINE/out/host_debug_unopt/dart-sdk/bin/dart \
before.json \
after.json
This should dump something like the following to the console.
+------------+----------------------------------------------------------+--------------+
| Library | Method | Diff (Bytes) |
+------------+----------------------------------------------------------+--------------+
| dart:async | new ZoneSpecification.from | +2136 |
| dart:async | runZoned | +1488 |
| dart:async | new _CustomZone | +927 |
| dart:async | runZoned.<anonymous closure> | +881 |
| dart:async | _rootFork | +504 |
| dart:async | _rootCreatePeriodicTimer | +500 |
| dart:async | _rootCreateTimer | +498 |
| dart:async | _rootRegisterUnaryCallback | +485 |
| dart:async | _rootRegisterBinaryCallback | +485 |
| dart:async | _rootRegisterCallback | +485 |
| dart:async | _rootPrint | +453 |
| dart:async | _CustomZone.fork | +396 |
| dart:async | _rootErrorCallback | +389 |
| dart:async | _CustomZone.bindUnaryCallbackGuarded | +368 |
| dart:async | _rootHandleUncaughtError | +342 |
| dart:async | _CustomZone.runBinary | +296 |
| dart:async | _CustomZone.runUnary | +293 |
| dart:async | _CustomZone.[] | +291 |
| dart:async | _CustomZone.registerCallback | +290 |
| dart:async | _CustomZone.run | +290 |
| dart:async | _CustomZone.registerUnaryCallback | +290 |
| dart:async | _CustomZone.registerBinaryCallback | +290 |
| dart:async | _CustomZone.runBinaryGuarded | +289 |
| dart:async | _CustomZone.runUnaryGuarded | +286 |
| dart:async | _RootZone.fork | +283 |
| dart:async | _CustomZone.bindCallback | +259 |
| dart:async | _CustomZone.bindUnaryCallback | +259 |
| dart:async | _CustomZone.bindUnaryCallback.<anonymous closure> | +248 |
| dart:async | _RootZone.bindUnaryCallback.<anonymous closure> | +248 |
| dart:async | _CustomZone.bindUnaryCallbackGuarded.<anonymous closure> | +248 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| | [Stub] Type Test Type: class 'PopupMenuEntry' | -128 |
| | [Stub] Type Test Type: class '_SyncIterator@0150898' | -128 |
| | [Stub] Type Test Type: class 'PopupMenuItem' | -128 |
| | [Stub] Type Test Type: class 'FormFieldState' | -128 |
| | [Stub] Type Test Type: class 'PopupMenuButton' | -128 |
| | [Stub] Type Test Type: class '_SyncIterator@0150898' | -131 |
| | [Stub] Type Test Type: class '_SplayTreeMapNode@3220832' | -139 |
| | [Stub] Type Test Type: class '_SplayTreeMapNode@3220832' | -165 |
| dart:io | new Directory | -211 |
| dart:io | new Link | -211 |
+------------+----------------------------------------------------------+--------------+
Total change +24036 bytes.