Enable lazy loading of AOTd assemblies (#6940)

Fixes: #6935 Context: dotnet/runtime#67024 Add support for enabling lazy loading of AOTd assemblies and their associated shared libraries, when targeting .NET6+. The feature is enabled by default when AOT is enabled for `Release` builds and can be disabled by setting the new `$(AndroidAotEnableLazyLoad)` MSBuild property to `false`. Performance gains are obvious, but their scale depends on where we look. Results of running a Hello World MAUI app on Pixel 6 Pro, with: See PR for full timing details. With: * `$(RuntimeIdentifier)`=android-arm64 * `$(AndroidEnablePreloadAssemblies)`=False * `$(AndroidUseAssemblyStore)`=True, `$(AndroidEnableAssemblyCompression)`=True | Scenario | Before | After | Δ | | ------------------------------------- | --------: | --------: | --------: | | `ActivityTaskManager: Displayed` time | 367.800 | 368.200 | +0.11% ✗ | | `JNIEnv.Initialize()` time | 6.221 | 5.367 | -13.73% ✓ | | Total native init time | 39.047 | 20.395 | -47.77% ✓ | With: * `$(RuntimeIdentifier)`=android-arm * `$(AndroidEnablePreloadAssemblies)`=True * `$(AndroidUseAssemblyStore)`=True, `$(AndroidEnableAssemblyCompression)`=True | Scenario | Before | After | Δ | | ------------------------------------- | --------: | --------: | --------: | | `ActivityTaskManager: Displayed` time | 490.600 | 475.000 | -3.18% ✓ | | `JNIEnv.Initialize()` time | 8.602 | 7.787 | -9.48% ✓ | | Total native init time | 47.726 | 27.156 | -43.10% ✓ |
dotnet · Apr 25, 2022 · 6dc426f · 6dc426f
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diff --git a/Documentation/guides/building-apps/build-properties.md b/Documentation/guides/building-apps/build-properties.md
@@ -75,6 +75,14 @@ Added in Xamarin.Android 10.1.
 
 The port that `aprofutil` should connect to when obtaining profiling data.
 
+## AndroidAotEnableLazyLoad
+
+Enable lazy (delayed) loading of AOT-d assemblies, instead of
+preloading them at the startup.  Defaults to `True` for Release builds
+with any form of AOT enabled.
+
+Introduced in .NET 6.
+
 ## AndroidApkDigestAlgorithm
 
 A string value which specifies

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/GeneratePackageManagerJava.cs b/src/Xamarin.Android.Build.Tasks/Tasks/GeneratePackageManagerJava.cs
@@ -75,6 +75,7 @@ public class GeneratePackageManagerJava : AndroidTask
 		public string Debug { get; set; }
 		public ITaskItem[] Environments { get; set; }
 		public string AndroidAotMode { get; set; }
+		public bool AndroidAotEnableLazyLoad { get; set; }
 		public bool EnableLLVM { get; set; }
 		public string HttpClientHandlerType { get; set; }
 		public string TlsProvider { get; set; }
@@ -408,6 +409,7 @@ void AddEnvironment ()
 				UsesMonoLLVM = EnableLLVM,
 				UsesAssemblyPreload = usesAssemblyPreload,
 				MonoAOTMode = aotMode.ToString ().ToLowerInvariant (),
+				AotEnableLazyLoad = AndroidAotEnableLazyLoad,
 				AndroidPackageName = AndroidPackageName,
 				BrokenExceptionTransitions = brokenExceptionTransitions,
 				PackageNamingPolicy = pnp,

diff --git a/...arin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/EnvironmentHelper.cs b/...arin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/EnvironmentHelper.cs
@@ -41,6 +41,7 @@ public sealed class ApplicationConfig
 		{
 			public bool   uses_mono_llvm;
 			public bool   uses_mono_aot;
+			public bool   aot_lazy_load;
 			public bool   uses_assembly_preload;
 			public bool   is_a_bundled_app;
 			public bool   broken_exception_transitions;
@@ -62,7 +63,7 @@ public sealed class ApplicationConfig
 			public uint   mono_components_mask;
 			public string android_package_name;
 		};
-		const uint ApplicationConfigFieldCount = 22;
+		const uint ApplicationConfigFieldCount = 23;
 
 		const string ApplicationConfigSymbolName = "application_config";
 		const string AppEnvironmentVariablesSymbolName = "app_environment_variables";
@@ -210,102 +211,108 @@ static ApplicationConfig ReadApplicationConfig (EnvironmentFile envFile)
 						ret.uses_mono_aot = ConvertFieldToBool ("uses_mono_aot", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 2: // uses_assembly_preload: bool / .byte
+					case 2:
+						// aot_lazy_load: bool / .byte
+						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
+						ret.uses_mono_aot = ConvertFieldToBool ("aot_lazy_load", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
+						break;
+
+					case 3: // uses_assembly_preload: bool / .byte
 						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
 						ret.uses_assembly_preload = ConvertFieldToBool ("uses_assembly_preload", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 3: // is_a_bundled_app: bool / .byte
+					case 4: // is_a_bundled_app: bool / .byte
 						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
 						ret.is_a_bundled_app = ConvertFieldToBool ("is_a_bundled_app", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 4: // broken_exception_transitions: bool / .byte
+					case 5: // broken_exception_transitions: bool / .byte
 						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
 						ret.broken_exception_transitions = ConvertFieldToBool ("broken_exception_transitions", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 5: // instant_run_enabled: bool / .byte
+					case 6: // instant_run_enabled: bool / .byte
 						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
 						ret.instant_run_enabled = ConvertFieldToBool ("instant_run_enabled", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 6: // jni_add_native_method_registration_attribute_present: bool / .byte
+					case 7: // jni_add_native_method_registration_attribute_present: bool / .byte
 						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
 						ret.jni_add_native_method_registration_attribute_present = ConvertFieldToBool ("jni_add_native_method_registration_attribute_present", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 7: // have_runtime_config_blob: bool / .byte
+					case 8: // have_runtime_config_blob: bool / .byte
 						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
 						ret.have_runtime_config_blob = ConvertFieldToBool ("have_runtime_config_blob", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 8: // have_assemblies_blob: bool / .byte
+					case 9: // have_assemblies_blob: bool / .byte
 						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
 						ret.have_assemblies_blob = ConvertFieldToBool ("have_assemblies_blob", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 9: // bound_stream_io_exception_type: byte / .byte
+					case 10: // bound_stream_io_exception_type: byte / .byte
 						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
 						ret.bound_stream_io_exception_type = ConvertFieldToByte ("bound_stream_io_exception_type", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 10: // package_naming_policy: uint32_t / .word | .long
+					case 11: // package_naming_policy: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.package_naming_policy = ConvertFieldToUInt32 ("package_naming_policy", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 11: // environment_variable_count: uint32_t / .word | .long
+					case 12: // environment_variable_count: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.environment_variable_count = ConvertFieldToUInt32 ("environment_variable_count", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 12: // system_property_count: uint32_t / .word | .long
+					case 13: // system_property_count: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.system_property_count = ConvertFieldToUInt32 ("system_property_count", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 13: // number_of_assemblies_in_apk: uint32_t / .word | .long
+					case 14: // number_of_assemblies_in_apk: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.number_of_assemblies_in_apk = ConvertFieldToUInt32 ("number_of_assemblies_in_apk", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 14: // bundled_assembly_name_width: uint32_t / .word | .long
+					case 15: // bundled_assembly_name_width: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.bundled_assembly_name_width = ConvertFieldToUInt32 ("bundled_assembly_name_width", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 15: // number_of_assembly_store_files: uint32_t / .word | .long
+					case 16: // number_of_assembly_store_files: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.number_of_assembly_store_files = ConvertFieldToUInt32 ("number_of_assembly_store_files", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 16: // number_of_dso_cache_entries: uint32_t / .word | .long
+					case 17: // number_of_dso_cache_entries: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.number_of_dso_cache_entries = ConvertFieldToUInt32 ("number_of_dso_cache_entries", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 17: // android_runtime_jnienv_class_token: uint32_t / .word | .long
+					case 18: // android_runtime_jnienv_class_token: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.number_of_dso_cache_entries = ConvertFieldToUInt32 ("android_runtime_jnienv_class_token", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 18: // jnienv_initialize_method_token: uint32_t / .word | .long
+					case 19: // jnienv_initialize_method_token: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.number_of_dso_cache_entries = ConvertFieldToUInt32 ("jnienv_initialize_method_token", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 19: // jnienv_registerjninatives_method_token: uint32_t / .word | .long
+					case 20: // jnienv_registerjninatives_method_token: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.number_of_dso_cache_entries = ConvertFieldToUInt32 ("jnienv_registerjninatives_method_token", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 20: // mono_components_mask: uint32_t / .word | .long
+					case 21: // mono_components_mask: uint32_t / .word | .long
 						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						ret.mono_components_mask = ConvertFieldToUInt32 ("mono_components_mask", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
 						break;
 
-					case 21: // android_package_name: string / [pointer type]
+					case 22: // android_package_name: string / [pointer type]
 						Assert.IsTrue (expectedPointerTypes.Contains (field [0]), $"Unexpected pointer field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						pointers.Add (field [1].Trim ());
 						break;

diff --git a/src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfig.cs b/src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfig.cs
@@ -26,6 +26,7 @@ sealed class ApplicationConfig
 	{
 		public bool   uses_mono_llvm;
 		public bool   uses_mono_aot;
+		public bool   aot_lazy_load;
 		public bool   uses_assembly_preload;
 		public bool   is_a_bundled_app;
 		public bool   broken_exception_transitions;

diff --git a/src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGenerator.cs b/src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGenerator.cs
@@ -156,6 +156,7 @@ sealed class XamarinAndroidBundledAssembly
 		public bool UsesMonoLLVM { get; set; }
 		public bool UsesAssemblyPreload { get; set; }
 		public string MonoAOTMode { get; set; }
+		public bool AotEnableLazyLoad { get; set; }
 		public string AndroidPackageName { get; set; }
 		public bool BrokenExceptionTransitions { get; set; }
 		public global::Android.Runtime.BoundExceptionType BoundExceptionType { get; set; }
@@ -192,6 +193,7 @@ public override void Init ()
 			var app_cfg = new ApplicationConfig {
 				uses_mono_llvm = UsesMonoLLVM,
 				uses_mono_aot = UsesMonoAOT,
+				aot_lazy_load = AotEnableLazyLoad,
 				uses_assembly_preload = UsesAssemblyPreload,
 				is_a_bundled_app = IsBundledApp,
 				broken_exception_transitions = BrokenExceptionTransitions,

diff --git a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
@@ -332,6 +332,7 @@ Copyright (C) 2011-2012 Xamarin. All rights reserved.
   <_AndroidAotStripLibraries Condition=" '$(_AndroidAotStripLibraries)' == '' And '$(AndroidIncludeDebugSymbols)' != 'true' ">True</_AndroidAotStripLibraries>
   <AndroidUseAssemblyStore Condition=" '$(AndroidUseAssemblyStore)' == '' and ('$(EmbedAssembliesIntoApk)' != 'true' or '$(AndroidIncludeDebugSymbols)' == 'true' or '$(BundleAssemblies)' == 'true') ">false</AndroidUseAssemblyStore>
   <AndroidUseAssemblyStore Condition=" '$(AndroidUseAssemblyStore)' == '' ">true</AndroidUseAssemblyStore>
+  <AndroidAotEnableLazyLoad Condition=" '$(AndroidAotEnableLazyLoad)' == '' And '$(AotAssemblies)' == 'true' And '$(AndroidIncludeDebugSymbols)' != 'true' ">True</AndroidAotEnableLazyLoad>
 </PropertyGroup>
 
 <!-- Do not resolve from the GAC under any circumstances in Mobile -->
@@ -1604,6 +1605,7 @@ because xbuild doesn't support framework reference assemblies.
     Manifest="$(IntermediateOutputPath)android\AndroidManifest.xml"
     Environments="@(AndroidEnvironment);@(LibraryEnvironments)"
     AndroidAotMode="$(AndroidAotMode)"
+    AndroidAotEnableLazyLoad="$(AndroidAotEnableLazyLoad)"
     EnableLLVM="$(EnableLLVM)"
     HttpClientHandlerType="$(AndroidHttpClientHandlerType)"
     TlsProvider="$(AndroidTlsProvider)"

diff --git a/src/monodroid/jni/application_dso_stub.cc b/src/monodroid/jni/application_dso_stub.cc
@@ -44,6 +44,7 @@ constexpr char android_package_name[] = "com.xamarin.test";
 const ApplicationConfig application_config = {
 	.uses_mono_llvm = false,
 	.uses_mono_aot = false,
+	.aot_lazy_load = false,
 	.uses_assembly_preload = false,
 	.is_a_bundled_app = false,
 	.broken_exception_transitions = false,

diff --git a/src/monodroid/jni/monodroid-glue-internal.hh b/src/monodroid/jni/monodroid-glue-internal.hh
@@ -38,10 +38,17 @@
 #undef NDEBUG_UNDEFINE
 #endif
 
+//#include <mono/utils/mono-publib.h>
 #include <mono/jit/mono-private-unstable.h>
 #include <mono/metadata/mono-private-unstable.h>
 #endif
 
+#if defined (NET6)
+// See https://github.com/dotnet/runtime/pull/67024
+// See https://github.com/xamarin/xamarin-android/issues/6935
+extern mono_bool mono_opt_aot_lazy_assembly_load;
+#endif // def NET6
+
 namespace xamarin::android::internal
 {
 	struct PinvokeEntry

diff --git a/src/monodroid/jni/monodroid-glue.cc b/src/monodroid/jni/monodroid-glue.cc
@@ -2144,6 +2144,8 @@ MonodroidRuntime::Java_mono_android_Runtime_initInternal (JNIEnv *env, jclass kl
 	jstring_wrapper &home = applicationDirs[SharedConstants::APP_DIRS_FILES_DIR_INDEX];
 
 #if defined (NET6)
+	mono_opt_aot_lazy_assembly_load = application_config.aot_lazy_load ? TRUE : FALSE;
+
 	{
 		MonoVMProperties monovm_props { home };
 

diff --git a/src/monodroid/jni/xamarin-app.hh b/src/monodroid/jni/xamarin-app.hh
@@ -202,6 +202,7 @@ struct ApplicationConfig
 {
 	bool uses_mono_llvm;
 	bool uses_mono_aot;
+	bool aot_lazy_load;
 	bool uses_assembly_preload;
 	bool is_a_bundled_app;
 	bool broken_exception_transitions;