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.dill
Save 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.