[.NET 10 rc1] regression in `Type.GetType()` performance on Android

[jonathanpeppers]

Description

I've been comparing startup time of the .NET MAUI project template on Android. .NET 9 vs .NET 10.

.NET 10 is slower, and one of the contributors is Type.GetType():

.NET  9:  30.52ms System.Private.CoreLib!System.Type.GetType(string,bool)
.NET 10: 146.77ms System.Private.CoreLib!System.Type.GetType(string,bool)

To verify we weren't just calling it more often, I added some logging in the Android workload and that did not appear to be the case. I did fix this related issue, I found on our side.

I estimate this degrades startup performance for the .NET MAUI template by around 115ms or so on a Pixel 5 device.

Comparing the two code paths, I can see new logic happening in .NET 10:

runtime/src/mono/System.Private.CoreLib/src/System/Type.Mono.cs

Lines 28 to 34 in c5e7fac

	[RequiresUnreferencedCode("The type might be removed")]
	[System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
	public static Type? GetType(string typeName, bool throwOnError, bool ignoreCase)
	{
	StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
	return GetType(typeName, null, null, throwOnError, ignoreCase, false, ref stackMark);
	}

While previously it just called:

runtime/src/mono/System.Private.CoreLib/src/System/Type.Mono.cs

Lines 28 to 34 in 4baf26c

	[RequiresUnreferencedCode("The type might be removed")]
	[System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
	public static Type? GetType(string typeName, bool throwOnError, bool ignoreCase)
	{
	StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
	return RuntimeType.GetType(typeName, throwOnError, ignoreCase, ref stackMark);
	}

Configuration

Build from vmr, .NET 10.0.100-rc.1.25412.102

Regression?

Yes

Data

dotnet-trace output: maui-type.gettype.zip

Analysis

Java interop's current implementation calls Type.GetType() a lot. .NET MAUI then makes many Java interop calls.

I made a BenchmarkDotNet project to test this, but the problem does not appear to occur on Windows desktop with CoreCLR. So, this could be specific to Mono or Android.

[MihuBot]

I'm a bot. Here is a possible related and/or duplicate issue (I may be wrong):

• [Perf][mono] GetType_[Non]FullyQualifiedNames regressions on 2/10/2025 10:18:46 PM #112763

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[jkotas]

Duplicate of #112763 . I am fixing it in #118761