Regression in flutter_gallery iOS release size

[zanderso]

On the PR here #139203 from @Hixie that rolled some pub deps forward, SkiaPerf is reporting a ~13MB regression in the iOS release size of the flutter_gallery.

https://flutter-flutter-perf.skia.org/e/?begin=1699661770&end=1701816185&keys=X002a387933ee8947522cae13fbd696c3&requestType=0&selected=commit%3D38182%26name%3D%252Carch%253Dintel%252Cbranch%253Dmaster%252Cconfig%253Ddefault%252Cdevice_type%253DiPhone_11%252Cdevice_version%253Dnone%252Chost_type%253Dmac%252Csub_result%253Drelease_size_bytes%252Ctest%253Dflutter_gallery_ios__compile%252C&xbaroffset=38181

Is this intentional or a benign side-effect of rolling the dependencies forward?

[Hixie]

Potential sources:

• shrine_images rolled from 2.0.1 to 2.0.2
• video_player moved from 2.2.11 to 2.8.1, a significant change

nothing else looks suspicious.

[Hixie]

shrine_images is unlikely to be the problem, the only change there was a trivial SDK version bump.

[Hixie]

@stuartmorgan any idea if bumping video_player that much (2.2.11 to 2.8.1) could be the cause of a ~13MB regression in iOS release size on flutter_gallery?

[stuartmorgan]

I'm not aware of any reason it would; that would certainly be surprising. video_player on iOS wraps the OS player, so doesn't involve any transitive dependencies, and we certainly didn't intentionally add 13 MB of code to the wrapper.

[jason-simmons]

#139203 updated Gallery's version of the url_launcher_ios plugin.

The new version of url_launcher_ios includes Swift code, and that brought in 10MB of Swift runtime libraries.

[stuartmorgan]

I assume that this is being measured pre-thinning? If so, I think we should just reset the baseline.

Is this our only size baseline? If so, we should seriously consider either replacing it, or at least adding a second one; the default project creation has been Swift/Kotlin for more than four years now, so the utility of a baseline that uses an Obj-C/Java template is questionable.

[zanderso]

The value comes from here:

https://github.com/flutter/flutter/blob/master/dev/devicelab/lib/tasks/perf_tests.dart#L1703

It's a straight up tar gz of the flutter build output directory, it looks like?

[jmagman]

Making the minimum iOS version 12.2 instead of 11.0 prevents the Swift runtime from being pulled in. https://developer.apple.com/documentation/xcode-release-notes/swift-5-release-notes-for-xcode-10_2#App-Thinning

[jmagman]

I've talked to @zanderso and the compressed app size isn't an accurate proxy for downloaded app size since the App Store encrypts and then recompresses the app.

When your app is approved for the App Store, it’s encrypted with Digital Rights Management (DRM) and recompressed. App Store file size for your binary may be larger than it is for the binary you uploaded in App Store Connect. The exact final size for your app can't be determined in advance.

https://developer.apple.com/help/app-store-connect/manage-builds/view-builds-and-metadata#view-the-file-sizes-of-a-build

One thing at a time though. #140188 will set the minimum deployment target for iOS compile perf tests to 12.2 which should fix some of the size regression related to the Swift runtime.

[jmagman]

I've talked to @zanderso and the compressed app size isn't an accurate proxy for downloaded app size since the App Store encrypts and then recompresses the app.

This comment suggests another reason measuring compressed app size is important is to validate that changes in Dart snapshot format and data layout do not change compression size.

flutter/dev/devicelab/lib/tasks/perf_tests.dart

Lines 1701 to 1702 in 0b6da5b

	// Validate changes in Dart snapshot format and data layout do not
	// change compression size. This also simulates the size of an IPA on iOS.

But then I looked at where we decided that matters and it was past-me and I can't remember why:
https://github.com/flutter/flutter/pull/109891/files#r954405126

[jmagman]

It's a straight up tar gz of the flutter build output directory, it looks like?

No, it's a tar gz of the app, not the whole output directory.

flutter/dev/devicelab/lib/tasks/perf_tests.dart

Lines 2224 to 2231 in 0b6da5b

	String? _findDarwinAppInBuildDirectory(String searchDirectory) {
	for (final FileSystemEntity entity in Directory(searchDirectory)
	.listSync(recursive: true)) {
	if (entity.path.endsWith('.app')) {
	return entity.path;
	}
	}
	return null;

flutter/dev/devicelab/lib/tasks/perf_tests.dart

Lines 1696 to 1703 in 0b6da5b

	final String? appPath =
	_findDarwinAppInBuildDirectory(buildDirectory.path);
	if (appPath == null) {
	throw 'Failed to find app bundle in ${buildDirectory.path}';
	}
	// Validate changes in Dart snapshot format and data layout do not
	// change compression size. This also simulates the size of an IPA on iOS.
	await exec('tar', <String>['-zcf', 'build/app.tar.gz', appPath]);

[zanderso]

@jmagman Thanks for investigating!

[jmagman]

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