[Java.Interop] remove IEnumerable iterators called at startup

[jonathanpeppers]

When profiling with adb setprop debug.mono.profile log:alloc, I
noticed the following allocations:

Allocation summary
     Bytes      Count  Average Type name
     84840        505      168 Java.Interop.JniRuntime.JniTypeManager.<CreateGetTypeSignaturesEnumerator>d__11
     24096        502       48 Android.Runtime.AndroidTypeManager.<GetSimpleReferences>d__1

This was using the Xamarin.Forms integration project in xamarin-android:

https://github.com/xamarin/xamarin-android/tree/master/tests/Xamarin.Forms-Performance-Integration

100K of memory allocations are a bit much, so seemed like it might help
to reduce these.

I made a version of both JniTypeManager.CreateTypeSignatures and
AndroidTypeManager.GetSimpleReferences that return a single value
instead of an IEnumerable and yield return.

Other general performance changes:

• Added [MethodImpl (MethodImplOptions.AggressiveInlining)] to
  JniTypeManager.AssertValid. It is called quite frequently.

• Removed a call to .GetTypeInfo(), as this was not needed. It wraps
  System.Type in another type that was probably originally used for
  netstandard 1.x compatibility.

See: https://github.com/mono/mono/blob/c5b88ec4f323f2bdb7c7d0a595ece28dae66579c/mcs/class/referencesource/mscorlib/system/reflection/introspectionextensions.cs#L24

Changes had to be made in both java.interop and xamarin-android for
this to work.

Results

I was able to see a startup improvement in a Release build of the
Xamarin.Forms integration project on a Pixel 3 XL:

Before:
01-08 14:53:34.926  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +779ms
01-08 14:53:38.892  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +764ms
01-08 14:53:42.859  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +753ms
01-08 14:53:46.795  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +748ms
01-08 14:53:50.792  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +764ms
01-08 14:53:54.759  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +756ms
01-08 14:53:58.726  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +764ms
01-08 14:54:02.675  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +749ms
01-08 14:54:06.691  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +759ms
01-08 14:54:10.641  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +749ms
Average(ms): 758.5
Std Err(ms): 3.0523215208537
Std Dev(ms): 9.65228815704684
After:
01-08 14:55:56.972  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +772ms
01-08 14:56:00.906  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +741ms
01-08 14:56:05.006  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +741ms
01-08 14:56:08.940  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +748ms
01-08 14:56:12.890  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +747ms
01-08 14:56:16.839  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +753ms
01-08 14:56:20.824  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +757ms
01-08 14:56:24.775  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +746ms
01-08 14:56:28.776  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +747ms
01-08 14:56:32.740  1473  1503 I ActivityTaskManager: Displayed Xamarin.Forms_Performance_Integration/xamarin.forms.performance.integration.MainActivity: +748ms
Average(ms): 750
Std Err(ms): 2.87904305089189
Std Dev(ms): 9.10433352249844

It seems like this might save ~8ms on startup?

There is also a good improvement to memory usage/allocations.

Looking at Mono's memory summary:

Before:
    Mono System:
    Working Set                    : 71008256
    Private Bytes                  : 601202688
    Virtual Bytes                  : 1306873856
After:
    Mono System:
    Working Set                    : 70774784
    Private Bytes                  : 552910848
    Virtual Bytes                  : 1302822912

Then the total GC summary:

Before:
Event: GC allocations          : 9340
After:
Event: GC allocations          : 8867

[jonathanpeppers]

Probably should wait on the results of the PR build here: dotnet/android#4102

[jonathanpeppers]

This change on the xamarin-android side seems to be OK: https://build.azdo.io/3368801

[jonathanpeppers]

An updated xamarin-android build is running here: https://build.azdo.io/3380356

[jonpryor]

Looks like we'll need to rebase the dotnet/android#4102 PR and rebase atop dotnet/android@e22be491, as it's getting lots of build failures due to NuGet.Common.

[jonathanpeppers]

New build is running at: https://build.azdo.io/3381690

[jonpryor]

My concern with this is that it's a semantic API break:

Currently a subclass would override Java.Interop.JniRuntime.JniTypeManager.GetSimpleReferences(), and a call to JniTypeManager.GetTypeSignature() will call GetSimpleReferences().

The xamarin-android repo currently does this.

After this PR, GetTypeSignature() will no longer call GetSimpleReferences(). This would break xamarin-android, except that dotnet/android#4102 adds a GetSimpleReferences() override as well.

Now on the "plus" side, (in theory) nobody is actually using this API, so changing semantics shouldn't actually break anybody.

That said, it instead results in documentation confusion. We'll have this class:

partial class JniTypeManager {
    public JniTypeSignature GetTypeSignature (Type type);
    protected virtual string GetSimpleReference (Type type);

    public IEnumerable<JniTypeSignature> GetTypeSignatures (Type type);
    protected virtual IEnumerable<string> GetSimpleReferences (Type type);
}

Which method needs to be overridden? One? Both?

I think it would be better if GetSimpleReference() delegated through GetSimpleReferences():

protected virtual string GetSimpleReference (Type type)
{
    return GetSimpleReferences (type).FirstOrDefault ();
}

That way existing code will not require a semantic change, but only a performance change.

[jonathanpeppers]

An updated xamarin-android build is running here: https://build.azdo.io/3384618

[jonathanpeppers]

I think that build looks OK, the one failing phase seems unrelated, a bunch of:

System.MissingMethodException : Method not found: 'Boolean System.String.Contains(Char)'.
at Xamarin.ProjectTools.XamarinProject.UpdateProjectFiles(String directory, IEnumerable`1 projectFiles, Boolean doNotCleanup)
at Xamarin.ProjectTools.ProjectBuilder.Save(XamarinProject project, Boolean doNotCleanupOnUpdate, Boolean saveProject) in /Users/builder/azdo/_work/3/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Common/ProjectBuilder.cs:line 47
at Xamarin.ProjectTools.ProjectBuilder.Build(XamarinProject project, Boolean doNotCleanupOnUpdate, String[] parameters, Boolean saveProject, Dictionary`2 environmentVariables) in /Users/builder/azdo/_work/3/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Common/ProjectBuilder.cs:line 68
at Xamarin.Android.Build.Tests.Aapt2Tests.Aapt2Disabled() in /Users/builder/azdo/_work/3/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Tasks/Aapt2Tests.cs:line 171

I sent this to see if it helps: dotnet/android#4124