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jonathanpeppersjonathanpeppers
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[Mono.Android] avoid System.Reflection.Emit usage for common calls
`dotnet new android` calls `JNINativeWrapper.CreateDelegate()` twice, while `dotnet new maui` ends up calling it 58 times during startup. This code path calls System.Reflection.Emit to generate a `System.Delegate` at runtime to be invoked. After some thought, it is possible to "hard code" common delegate types and avoid SRE: private static Delegate CreateBuiltInDelegate (Delegate dlg, Type delegateType) { switch (delegateType.Name) { case nameof (_JniMarshal_PP_V): { _JniMarshal_PP_V callback = (_JniMarshal_PP_V) Delegate.CreateDelegate (typeof (_JniMarshal_PP_V), dlg.Target, dlg.Method); _JniMarshal_PP_V result = (jnienv, klazz) => { JNIEnv.WaitForBridgeProcessing (); try { callback (jnienv, klazz); } catch (Exception e) { bool filter = Debugger.IsAttached || !JNIEnv.PropagateExceptions; if (filter && JNIEnv.mono_unhandled_exception != null) { JNIEnv.mono_unhandled_exception (e); } AndroidEnvironment.UnhandledException (e); if (filter) throw; } }; return result; } // etc. `dotnet new maui`'s startup can be covered if we hardcoded: _JniMarshal_PP_V _JniMarshal_PPI_V _JniMarshal_PPL_L _JniMarshal_PPL_V _JniMarshal_PPL_Z _JniMarshal_PPII_V _JniMarshal_PPLI_V _JniMarshal_PPLL_V _JniMarshal_PPLL_Z _JniMarshal_PPIIL_V _JniMarshal_PPILL_V _JniMarshal_PPLIL_Z _JniMarshal_PPLLL_L _JniMarshal_PPLLL_Z _JniMarshal_PPIIII_V _JniMarshal_PPLLLL_V _JniMarshal_PPLIIII_V _JniMarshal_PPZIIII_V _JniMarshal_PPLIIIIIIII_V Then System.Reflection.Emit isn't used at all. Other changes: * `TypeManager.GetActivateHandler()` needs to use `_JniMarshal_PPLLLL_V` instead of `Action<IntPtr, IntPtr, IntPtr, IntPtr, IntPtr, IntPtr>`, so the fast path can be used. * Added a log message for `debug.mono.log assembly`: Falling back to System.Reflection.Emit for delegate type '{delegateType}': {dlg.Method} * I was also able to remove `mono_unhandled_exception_method` from `JNINativeWrapper` as we already has this value in `JNIEnv`. ~~ Results ~~ Testing `dotnet new maui` with version: msbuild Xamarin.Android.sln -t:InstallMaui -bl -p:MauiVersion=6.0.200-preview.13.2536 A `Release` build on a Pixel 5 device, total startup time: Before: 01-21 11:58:39.030 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s83ms 01-21 11:58:41.297 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s127ms 01-21 11:58:43.429 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s68ms 01-21 11:58:45.702 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s113ms 01-21 11:58:47.906 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s125ms 01-21 11:58:50.082 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s92ms 01-21 11:58:52.297 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s133ms 01-21 11:58:54.465 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s102ms 01-21 11:58:56.673 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s126ms 01-21 11:58:58.848 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s94ms Average(ms): 1106.3 Std Err(ms): 6.91865433287267 Std Dev(ms): 21.8787060352704 After: 01-21 12:00:33.312 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s61ms 01-21 12:00:35.513 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s79ms 01-21 12:00:37.724 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s85ms 01-21 12:00:39.928 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s83ms 01-21 12:00:42.117 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s60ms 01-21 12:00:44.337 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s59ms 01-21 12:00:46.612 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s106ms 01-21 12:00:48.782 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s47ms 01-21 12:00:51.018 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s75ms 01-21 12:00:53.200 1867 2226 I ActivityTaskManager: Displayed com.companyname.bar/crc6474063b540de74d1e.MainActivity: +1s53ms Average(ms): 1070.8 Std Err(ms): 5.68584988272544 Std Dev(ms): 17.9802360632137 This might save ~35ms on average? If I time the message for one call, such as: 01-21 12:14:01.132 29819 29819 I monodroid-timing: Runtime.register: registering type `Microsoft.Maui.MauiApplication, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null` 01-21 12:14:01.150 29819 29819 I monodroid-timing: Runtime.register: end time; elapsed: 0s:17::794845 https://github.com/dotnet/maui/blob/bfba62ed796d3416c4fcaa7cfbea86dc8d5e04c2/src/Compatibility/ControlGallery/src/Android/MainApplication.cs The result is: Before: 01-21 13:21:22.261 9359 9359 I monodroid-timing: Runtime.register: end time; elapsed: 0s:23::868440 01-21 13:21:24.446 9424 9424 I monodroid-timing: Runtime.register: end time; elapsed: 0s:23::875159 01-21 13:21:26.639 9497 9497 I monodroid-timing: Runtime.register: end time; elapsed: 0s:23::829742 01-21 13:21:28.842 9570 9570 I monodroid-timing: Runtime.register: end time; elapsed: 0s:24::165211 01-21 13:21:31.021 9631 9631 I monodroid-timing: Runtime.register: end time; elapsed: 0s:23::976721 01-21 13:21:33.221 9697 9697 I monodroid-timing: Runtime.register: end time; elapsed: 0s:24::237034 01-21 13:21:35.418 9759 9759 I monodroid-timing: Runtime.register: end time; elapsed: 0s:23::857346 01-21 13:21:37.585 9821 9821 I monodroid-timing: Runtime.register: end time; elapsed: 0s:23::872138 01-21 13:21:39.805 9884 9884 I monodroid-timing: Runtime.register: end time; elapsed: 0s:23::840107 01-21 13:21:42.014 9952 9952 I monodroid-timing: Runtime.register: end time; elapsed: 0s:23::723805 Average(ms): 23.9245703 Std Err(ms): 0.0502830551065224 Std Dev(ms): 0.159008981848371 After: 01-21 13:22:28.004 10226 10226 I monodroid-timing: Runtime.register: end time; elapsed: 0s:18::12345 01-21 13:22:30.261 10298 10298 I monodroid-timing: Runtime.register: end time; elapsed: 0s:18::338022 01-21 13:22:32.443 10362 10362 I monodroid-timing: Runtime.register: end time; elapsed: 0s:18::56251 01-21 13:22:34.664 10427 10427 I monodroid-timing: Runtime.register: end time; elapsed: 0s:17::997397 01-21 13:22:36.902 10497 10497 I monodroid-timing: Runtime.register: end time; elapsed: 0s:17::787554 01-21 13:22:39.117 10563 10563 I monodroid-timing: Runtime.register: end time; elapsed: 0s:17::801772 01-21 13:22:41.306 10630 10630 I monodroid-timing: Runtime.register: end time; elapsed: 0s:18::28752 01-21 13:22:43.552 10695 10695 I monodroid-timing: Runtime.register: end time; elapsed: 0s:18::75522 01-21 13:22:45.761 10759 10759 I monodroid-timing: Runtime.register: end time; elapsed: 0s:17::958075 01-21 13:22:47.978 10823 10823 I monodroid-timing: Runtime.register: end time; elapsed: 0s:18::961773 Average(ms): 18.1017463 Std Err(ms): 0.107071213504746 Std Dev(ms): 0.338588906513177 Saving ~5.8ms for this one call.
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‎src/Mono.Android/Android.Runtime/JNIEnv.cs

Lines changed: 11 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -56,7 +56,7 @@ public static partial class JNIEnv {
5656
internal static bool PropagateExceptions;
5757

5858
internal static bool IsRunningOnDesktop;
59-
internal static bool LogTypemapMissStackTrace;
59+
internal static bool LogAssemblyCategory;
6060

6161
static AndroidRuntime? androidRuntime;
6262
static BoundExceptionType BoundExceptionType;
@@ -67,7 +67,7 @@ public static partial class JNIEnv {
6767
internal static AndroidValueManager? AndroidValueManager;
6868

6969
[DllImport (AndroidRuntime.InternalDllName, CallingConvention = CallingConvention.Cdecl)]
70-
extern static void monodroid_log (LogLevel level, LogCategories category, string message);
70+
internal extern static void monodroid_log (LogLevel level, LogCategories category, string message);
7171

7272
[DllImport (AndroidRuntime.InternalDllName, CallingConvention = CallingConvention.Cdecl)]
7373
internal extern static IntPtr monodroid_timing_start (string? message);
@@ -149,7 +149,7 @@ internal static unsafe void Initialize (JnienvInitializeArgs* args)
149149
partial_timing_sequence = monodroid_timing_start (null);
150150
}
151151

152-
LogTypemapMissStackTrace = (args->logCategories & (uint)LogCategories.Assembly) != 0;
152+
LogAssemblyCategory = (args->logCategories & (uint)LogCategories.Assembly) != 0;
153153

154154
gref_gc_threshold = args->grefGcThreshold;
155155

@@ -246,6 +246,7 @@ static void ManualJavaObjectDispose (Java.Lang.Object obj)
246246
#else // NETCOREAPP
247247
internal static Action<Exception> mono_unhandled_exception = null!;
248248
#endif // NETCOREAPP
249+
internal static MethodInfo? mono_unhandled_exception_method = null;
249250

250251
#if !NETCOREAPP
251252
static Action<AppDomain, UnhandledExceptionEventArgs> AppDomain_DoUnhandledException = null!;
@@ -254,10 +255,13 @@ static void ManualJavaObjectDispose (Java.Lang.Object obj)
254255
static void Initialize ()
255256
{
256257
if (mono_unhandled_exception == null) {
257-
var mono_UnhandledException = typeof (System.Diagnostics.Debugger)
258+
mono_unhandled_exception_method = typeof (System.Diagnostics.Debugger)
258259
.GetMethod ("Mono_UnhandledException", BindingFlags.NonPublic | BindingFlags.Static);
259-
if (mono_UnhandledException != null)
260-
mono_unhandled_exception = (Action<Exception>) Delegate.CreateDelegate (typeof(Action<Exception>), mono_UnhandledException);
260+
if (mono_unhandled_exception_method != null)
261+
mono_unhandled_exception = (Action<Exception>) Delegate.CreateDelegate (typeof(Action<Exception>), mono_unhandled_exception_method);
262+
}
263+
if (mono_unhandled_exception_method == null && mono_unhandled_exception != null) {
264+
mono_unhandled_exception_method = mono_unhandled_exception.Method;
261265
}
262266

263267
#if !NETCOREAPP
@@ -737,7 +741,7 @@ internal static void LogTypemapTrace (StackTrace st)
737741
}
738742

739743
if (ret == IntPtr.Zero) {
740-
if (LogTypemapMissStackTrace) {
744+
if (LogAssemblyCategory) {
741745
monodroid_log (LogLevel.Warn, LogCategories.Default, $"typemap: failed to map managed type to Java type: {type.AssemblyQualifiedName} (Module ID: {type.Module.ModuleVersionId}; Type token: {type.MetadataToken})");
742746
LogTypemapTrace (new StackTrace (true));
743747
}

‎src/Mono.Android/Android.Runtime/JNINativeWrapper.cs

Lines changed: 13 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -5,25 +5,16 @@
55
using System.Threading;
66

77
namespace Android.Runtime {
8-
public static class JNINativeWrapper {
8+
public static partial class JNINativeWrapper {
99

10-
static MethodInfo? mono_unhandled_exception_method;
1110
static MethodInfo? exception_handler_method;
1211
static MethodInfo? wait_for_bridge_processing_method;
1312

1413
static void get_runtime_types ()
1514
{
1615
if (exception_handler_method != null)
1716
return;
18-
#if MONOANDROID1_0
19-
mono_unhandled_exception_method = typeof (System.Diagnostics.Debugger).GetMethod (
20-
"Mono_UnhandledException", BindingFlags.NonPublic | BindingFlags.Static);
21-
if (mono_unhandled_exception_method == null)
22-
AndroidEnvironment.FailFast ("Cannot find System.Diagnostics.Debugger.Mono_UnhandledException");
23-
#endif
24-
#if NETCOREAPP
25-
mono_unhandled_exception_method = JNIEnv.mono_unhandled_exception.Method;
26-
#endif // NETCOREAPP
17+
2718
exception_handler_method = typeof (AndroidEnvironment).GetMethod (
2819
"UnhandledException", BindingFlags.NonPublic | BindingFlags.Static);
2920
if (exception_handler_method == null)
@@ -45,6 +36,15 @@ public static Delegate CreateDelegate (Delegate dlg)
4536

4637
get_runtime_types ();
4738

39+
var delegateType = dlg.GetType ();
40+
var result = CreateBuiltInDelegate (dlg, delegateType);
41+
if (result != null)
42+
return result;
43+
44+
if (JNIEnv.LogAssemblyCategory) {
45+
JNIEnv.monodroid_log (LogLevel.Warn, LogCategories.Default, $"Falling back to System.Reflection.Emit for delegate type '{delegateType}': {dlg.Method}");
46+
}
47+
4848
var ret_type = dlg.Method.ReturnType;
4949
var parameters = dlg.Method.GetParameters ();
5050
var param_types = new Type [parameters.Length];
@@ -73,10 +73,10 @@ public static Delegate CreateDelegate (Delegate dlg)
7373
ig.Emit (OpCodes.Leave, label);
7474

7575
bool filter = Debugger.IsAttached || !JNIEnv.PropagateExceptions;
76-
if (filter && mono_unhandled_exception_method != null) {
76+
if (filter && JNIEnv.mono_unhandled_exception_method != null) {
7777
ig.BeginExceptFilterBlock ();
7878

79-
ig.Emit (OpCodes.Call, mono_unhandled_exception_method);
79+
ig.Emit (OpCodes.Call, JNIEnv.mono_unhandled_exception_method);
8080
ig.Emit (OpCodes.Ldc_I4_1);
8181
ig.BeginCatchBlock (null!);
8282
} else {

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