.NET: SingleView app size

[rolfbjarne]

App sizes are currently significantly bigger with .NET 6 with a very simple hello world app.

Test case

• Checkout xamarin-macios
• Execute:

cd tests/dotnet
make compare

This will build a very simple hello world app for both .NET 6 and the old-style Xamarin.iOS and generate a report in markdown format. This can be pasted into the issue (e.g. for each preview) so the progress can be tracked.

Known Issues

• The (dynamic) registrar isn't removed when enabling all the optimizations
  • The dynamic registrar requires a larger subset of System.Reflection API (see below)
• The .NET 6 version does not strip the native executable.
• The mono-cil-strip tool is not run on the final assemblies (it's not available without the mono SDK installed)
  • All assemblies still have their IL even when it's not required (FullAOT by default for device builds)
  • Tracked, among other tools, in Packaging & redistribution of mdoc.exe & mono-symbolicate in a .NET 6 world? runtime#35852 @marek-safar recently mentioned it was being looked at for Blazor (there might be another issue I missed)

Historical

App sizes

Xamarin.iOS

du -hs size-comparison/MySingleView/oldnet/bin/iPhone/Release/MySingleView.app
4.4M size-comparison/MySingleView/oldnet/bin/iPhone/Release/MySingleView.app

.NET 6

du -hs size-comparison/MySingleView/dotnet/bin/iPhone/Release/net6.0-ios/ios-arm64/*.app
27M size-comparison/MySingleView/dotnet/bin/iPhone/Release/net6.0-ios/ios-arm64/MySingleView.app

Assembly sizes

Xamarin.iOS

ls -lahS size-comparison/MySingleView/oldnet/bin/iPhone/Release/MySingleView.app/.dll size-comparison/MySingleView/oldnet/bin/iPhone/Release/MySingleView.app/.exe
-rw-r--r-- 1 rolf wheel 397K Dec 9 19:04 size-comparison/MySingleView/oldnet/bin/iPhone/Release/MySingleView.app/mscorlib.dll
-rw-r--r-- 1 rolf wheel 54K Dec 9 19:04 size-comparison/MySingleView/oldnet/bin/iPhone/Release/MySingleView.app/Xamarin.iOS.dll
-rw-r--r-- 1 rolf wheel 4.5K Dec 9 19:04 size-comparison/MySingleView/oldnet/bin/iPhone/Release/MySingleView.app/MySingleView.exe
-rw-r--r-- 1 rolf wheel 4.5K Dec 9 19:05 size-comparison/MySingleView/oldnet/bin/iPhone/Release/MySingleView.app/System.dll

.NET 6

ls -lahS size-comparison/MySingleView/dotnet/bin/iPhone/Release/net6.0-ios/ios-arm64/.app/.dll
-rw-r--r-- 1 rolf wheel 1.3M Dec 9 19:05 size-comparison/MySingleView/dotnet/bin/iPhone/Release/net6.0-ios/ios-arm64/MySingleView.app/System.Private.CoreLib.dll
-rw-r--r-- 1 rolf wheel 161K Dec 9 19:05 size-comparison/MySingleView/dotnet/bin/iPhone/Release/net6.0-ios/ios-arm64/MySingleView.app/Xamarin.iOS.dll
-rw-r--r-- 1 rolf wheel 17K Dec 9 19:05 size-comparison/MySingleView/dotnet/bin/iPhone/Release/net6.0-ios/ios-arm64/MySingleView.app/System.Runtime.dll
-rw-r--r-- 1 rolf wheel 16K Dec 9 19:05 size-comparison/MySingleView/dotnet/bin/iPhone/Release/net6.0-ios/ios-arm64/MySingleView.app/System.Runtime.Serialization.Formatters.dll
-rw-r--r-- 1 rolf wheel 5.0K Dec 9 19:05 size-comparison/MySingleView/dotnet/bin/iPhone/Release/net6.0-ios/ios-arm64/MySingleView.app/MySingleView.dll

---

There are multiple issues here:

• The .NET 6 version has unnecessary dylibs (because it's linking libraries statically). fix
• The .NET 6 version does not strip the native executable.
• The .NET 6 version's assemblies are much bigger (the linker doesn't remove as much): 1,5 MB vs 460 KB.

Additionally the .NET 6 version takes twice as long to compile (22s vs 11s on my machine), but that's a different issue (filed as #10251).

[spouliot]

Shameless plug but you might want to use https://github.com/spouliot/dotnet-tools/tree/master/app-compare to compare the size of the current/dotnet apps

[spouliot]

Additionally the .NET 6 version takes twice as long to compile (22s vs 11s on my machine), but that's a different issue.

Considering most of the device build time comes from the AOT compiler (at least in current form) then a 2x build time increase is not so bad as there's more than 3x more managed code (1,5 MB vs 460 KB) to AOT. IOW we can consider this the "same issue", unless the time increase comes from elsewhere.

[marek-safar]

It looks like you don't have some of the feature switched enabled, see https://github.com/dotnet/runtime/blob/master/docs/workflow/trimming/feature-switches.md. I'm not saying that's all that needs to be done but it's a good start ;-)

[spouliot]

Application Comparer

• A oldnet/bin/iPhone/Release/MySingleView.app
• B dotnet/bin/iPhone/Release/net6.0-ios/ios-arm64/MySingleView.app

Directories / Files	A	B	diff	%
.//_CodeSignature
.//
embedded.mobileprovision	12,218	12,218	0	0.0%
Info.plist	1,055	1,055	0	0.0%
libmonosgen-2.0.dylib	0	3,177,312	3,177,312	-
libSystem.IO.Compression.Native.dylib	0	827,104	827,104	-
libSystem.Native.dylib	0	123,040	123,040	-
libSystem.Net.Security.Native.dylib	0	72,016	72,016	-
libSystem.Security.Cryptography.Native.Apple.dylib	0	80,656	80,656	-
libxamarin-debug.dylib	0	623,856	623,856	-
libxamarin.dylib	0	425,408	425,408	-
mscorlib.aotdata.arm64	296,872	0	-296,872	-100.0%
mscorlib.dll	406,528	0	-406,528	-100.0%
MySingleView	3,748,192	18,281,760	14,533,568	387.7%
MySingleView.aotdata.arm64	816	1,136	320	39.2%
MySingleView.dll	0	5,120	5,120	-
MySingleView.exe	4,608	0	-4,608	-100.0%
MySingleView.pdb	0	9,720	9,720	-
PkgInfo	8	8	0	0.0%
System.aotdata.arm64	752	0	-752	-100.0%
System.dll	4,608	0	-4,608	-100.0%
System.Private.CoreLib.aotdata.arm64	0	3,082,504	3,082,504	-
System.Private.CoreLib.dll	0	1,391,616	1,391,616	-
System.Runtime.aotdata.arm64	0	504	504	-
System.Runtime.dll	0	17,408	17,408	-
System.Runtime.Serialization.Formatters.aotdata.arm64	0	1,144	1,144	-
System.Runtime.Serialization.Formatters.dll	0	15,872	15,872	-
Xamarin.iOS.aotdata.arm64	35,048	319,112	284,064	810.5%
Xamarin.iOS.dll	55,296	163,840	108,544	196.3%
Statistics
Native subtotal	3,748,192	18,281,760	14,533,568	387.7%
Executable	3,748,192	18,281,760	14,533,568	387.7%
AOT data *.aotdata	0	0	0	-
Managed *.dll/exe	471,040	1,593,856	1,122,816	238.4%
TOTAL	4,571,262	28,640,968	24,069,706	526.5%

[spouliot]

other issues

• debugging symbol files, like MySingleView.pdb, should not be copied to release .app
• otool -L MySingleView does not show libicu* nor is there any data files. AFAIK those are required for globalization of net5+ apps (and the existing oldnet app has globalization support)

update: both issues are fixed with P4

[marek-safar]

@spouliot could you share the binaries?

[spouliot]

@marek-safar yes but likely not today. My main internet connection is down :( and I'm waiting for a new modem to be delivered. Trying to limit myself to low bandwidth (cellular) tasks.

[rolfbjarne]

It looks like you don't have some of the feature switched enabled, see https://github.com/dotnet/runtime/blob/master/docs/workflow/trimming/feature-switches.md. I'm not saying that's all that needs to be done but it's a good start ;-)

#10250 - that shaves off a good chunk.

[rolfbjarne]

@marek-safar

@spouliot could you share the binaries?

dotnet.zip
oldnet.zip

That's after #10250, so the runtime switches have been toggled for these apps.

[rolfbjarne]

Additionally the .NET 6 version takes twice as long to compile (22s vs 11s on my machine), but that's a different issue.

Considering most of the device build time comes from the AOT compiler (at least in current form) then a 2x build time increase is not so bad as there's more than 3x more managed code (1,5 MB vs 460 KB) to AOT. IOW we can consider this the "same issue", unless the time increase comes from elsewhere.

I filed #10251 for this: just executing the .NET 6 linker takes longer than linking + AOT compilation + native compilation used to.