Support for Android "Profiled AOT" in .NET 6

[jonathanpeppers]

This feature in Xamarin.Android is also known as "Startup Tracing":

https://devblogs.microsoft.com/xamarin/faster-android-startup-times-with-startup-tracing/

Yet another name for this might be "profile guided optimization".

For .NET 6, we'd like users be able to do something like the following in Release builds:

<RunAOTCompilation>true</RunAOTCompilation>
<UseProfiledAOT>true</UseProfiledAOT>

This would use a built-in profile that the Android workload provides as well as the .NET MAUI workload. Recording a custom profile for a developer's app is probably not something we need in .NET 6. However, the Android & .NET MAUI teams would need to be able to record profiles. .NET MAUI's startup path is still quite a bit in flux, so ideally we would be automate the creation of the built-in MAUI profile.

There are a few pieces missing from dotnet/runtime at the moment:

1. libmono-profiler-aot.so
2. aprofutil
3. MonoAOTCompiler.AotProfilePath only accepts 1 value:

runtime/src/tasks/AotCompilerTask/MonoAOTCompiler.cs

Lines 111 to 114 in ce3447c

	/// <summary>
	/// File to use for profile-guided optimization, *only* the methods described in the file will be AOT compiled.
	/// </summary>
	public string? AotProfilePath { get; set; }

For .NET 6, I think we can take a simple approach:

1. Build & ship libmono-profiler-aot.so in the Android runtime packs.
2. The Android workload can ship a aprofutil from mono/mono. We can emit warnings that mention recording custom AOT profiles is an experimental feature.
3. We can emit profile-only,profile=foo.aprof for %(AotArguments) in the Android MSBuild targets until there is a different way.

These would get us by for now.

In the long run, recording custom AOT profiles might be something that dotnet-trace / diagnostics should support.

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See info in area-owners.md if you want to be subscribed.

Issue Details

---

This feature in Xamarin.Android is also known as "Startup Tracing":

https://devblogs.microsoft.com/xamarin/faster-android-startup-times-with-startup-tracing/

Yet another name for this might be "profile guided optimization".

For .NET 6, we'd like users be able to do something like the following in Release builds:

<RunAOTCompilation>true</RunAOTCompilation>
<UseProfiledAOT>true</UseProfiledAOT>

This would use a built-in profile that the Android workload provides as well as the .NET MAUI workload. Recording a custom profile for a developer's app is probably not something we need in .NET 6. However, the Android & .NET MAUI teams would need to be able to record profiles. .NET MAUI's startup path is still quite a bit in flux at the moment, so ideally we would be automate the creation of the built-in MAUI profile.

There are a few pieces missing from dotnet/runtime at the moment:

1. libmono-profiler-aot.so
2. aprofutil
3. MonoAOTCompiler.AotProfilePath only accepts 1 value:

runtime/src/tasks/AotCompilerTask/MonoAOTCompiler.cs

Lines 111 to 114 in ce3447c

	/// <summary>
	/// File to use for profile-guided optimization, *only* the methods described in the file will be AOT compiled.
	/// </summary>
	public string? AotProfilePath { get; set; }

For .NET 6, I think we can take a simple approach:

1. Build & ship libmono-profiler-aot.so in the Android runtime packs.
2. The Android workload can ship a aprofutil from mono/mono. We can emit warnings that mention recording custom AOT profiles is an experimental feature.
3. We can emit, profile-only,profile=foo.aprof for %(AotArguments) in the Android MSBuild targets until there is a different way.

These would get us by for now.

In the long run, recording custom AOT profiles might be something that dotnet-trace / diagnostics should support.

Author:	jonathanpeppers
Assignees:	-
Labels:	area-Diagnostics-coreclr, untriaged
Milestone:	-

Tagging subscribers to this area:
See info in area-owners.md if you want to be subscribed.

Issue Details

---

This feature in Xamarin.Android is also known as "Startup Tracing":

https://devblogs.microsoft.com/xamarin/faster-android-startup-times-with-startup-tracing/

Yet another name for this might be "profile guided optimization".

For .NET 6, we'd like users be able to do something like the following in Release builds:

<RunAOTCompilation>true</RunAOTCompilation>
<UseProfiledAOT>true</UseProfiledAOT>

This would use a built-in profile that the Android workload provides as well as the .NET MAUI workload. Recording a custom profile for a developer's app is probably not something we need in .NET 6. However, the Android & .NET MAUI teams would need to be able to record profiles. .NET MAUI's startup path is still quite a bit in flux at the moment, so ideally we would be automate the creation of the built-in MAUI profile.

There are a few pieces missing from dotnet/runtime at the moment:

1. libmono-profiler-aot.so
2. aprofutil
3. MonoAOTCompiler.AotProfilePath only accepts 1 value:

runtime/src/tasks/AotCompilerTask/MonoAOTCompiler.cs

Lines 111 to 114 in ce3447c

	/// <summary>
	/// File to use for profile-guided optimization, *only* the methods described in the file will be AOT compiled.
	/// </summary>
	public string? AotProfilePath { get; set; }

For .NET 6, I think we can take a simple approach:

1. Build & ship libmono-profiler-aot.so in the Android runtime packs.
2. The Android workload can ship a aprofutil from mono/mono. We can emit warnings that mention recording custom AOT profiles is an experimental feature.
3. We can emit, profile-only,profile=foo.aprof for %(AotArguments) in the Android MSBuild targets until there is a different way.

These would get us by for now.

In the long run, recording custom AOT profiles might be something that dotnet-trace / diagnostics should support.

Author:	jonathanpeppers
Assignees:	-
Labels:	untriaged, area-VM-meta-mono
Milestone:	-

[akoeplinger]

So we need to do two things:

• enable build of libmono-profiler-aot.so in mono.proj (it's already done for Browser)
• support multiple arguments for AotProfilePath in MonoAOTCompiler - done in [MonoAOTCompiler] accept more than one AotProfilePath #57111