[Mono.Android] Guard GREF/WREF logging P/Invokes behind Logger.LogGlobalRef check

The AndroidObjectReferenceManager overrides for CreateGlobalReference,
DeleteGlobalReference, CreateWeakGlobalReference, and
DeleteWeakGlobalReference were unconditionally calling native logging
P/Invokes (_monodroid_gref_log_new, _monodroid_gref_log_delete,
_monodroid_weak_gref_new, _monodroid_weak_gref_delete) on every
invocation, even when GREF logging was disabled.

While the native side does an early return when LOG_GREF is off, the
managed-to-native transition itself has measurable overhead that adds
up when creating/deleting many references in a tight loop (e.g. during
GC bridge processing).

This change wraps the P/Invoke calls in `if (Logger.LogGlobalRef)`
guards, matching the pattern already used for local reference logging
(CreateLocalReference, DeleteLocalReference, etc.).

Note: the native counters (gc_gref_count, gc_weak_gref_count) will not
be updated when logging is off. These counters are only used for
logging output and the GREF threshold GC trigger, both of which are
only relevant when logging is enabled.

Author: simonrozsival

src/Mono.Android/Android.Runtime/AndroidRuntime.cs

@@ -176,18 +176,19 @@ public override void WriteGlobalReferenceLine (string format, params object?[] a
 
 		public override JniObjectReference CreateGlobalReference (JniObjectReference value)
 		{
-			var r     = base.CreateGlobalReference (value);
+			var r = base.CreateGlobalReference (value);
 
-			var log		= Logger.LogGlobalRef;
-			var ctype	= log ? GetObjectRefType (value.Type) : (byte) '*';
-			var ntype	= log ? GetObjectRefType (r.Type) : (byte) '*';
-			var tname = log ? Thread.CurrentThread.Name : null;
-			var tid   = log ? Thread.CurrentThread.ManagedThreadId : 0;
-			var from  = log ? new StringBuilder (new StackTrace (true).ToString ()) : null;
-			int gc 		= RuntimeNativeMethods._monodroid_gref_log_new (value.Handle, ctype, r.Handle, ntype, tname, tid, from, 1);
-			if (gc >= JNIEnvInit.gref_gc_threshold) {
-				Logger.Log (LogLevel.Warn, "monodroid-gc", gc + " outstanding GREFs. Performing a full GC!");
-				System.GC.Collect ();
+			if (Logger.LogGlobalRef) {
+				var ctype = GetObjectRefType (value.Type);
+				var ntype = GetObjectRefType (r.Type);
+				var tname = Thread.CurrentThread.Name;
+				var tid   = Thread.CurrentThread.ManagedThreadId;
+				var from  = new StringBuilder (new StackTrace (true).ToString ());
+				int gc    = RuntimeNativeMethods._monodroid_gref_log_new (value.Handle, ctype, r.Handle, ntype, tname, tid, from, 1);
+				if (gc >= JNIEnvInit.gref_gc_threshold) {
+					Logger.Log (LogLevel.Warn, "monodroid-gc", gc + " outstanding GREFs. Performing a full GC!");
+					System.GC.Collect ();
+				}
 			}
 
 			return r;
@@ -206,12 +207,13 @@ static byte GetObjectRefType (JniObjectReferenceType type)
 
 		public override void DeleteGlobalReference (ref JniObjectReference value)
 		{
-			var log		= Logger.LogGlobalRef;
-			var ctype	= log ? GetObjectRefType (value.Type) : (byte) '*';
-			var tname = log ? Thread.CurrentThread.Name : null;
-			var tid   = log ? Thread.CurrentThread.ManagedThreadId : 0;
-			var from  = log ? new StringBuilder (new StackTrace (true).ToString ()) : null;
-			RuntimeNativeMethods._monodroid_gref_log_delete (value.Handle, ctype, tname, tid, from, 1);
+			if (Logger.LogGlobalRef) {
+				var ctype = GetObjectRefType (value.Type);
+				var tname = Thread.CurrentThread.Name;
+				var tid   = Thread.CurrentThread.ManagedThreadId;
+				var from  = new StringBuilder (new StackTrace (true).ToString ());
+				RuntimeNativeMethods._monodroid_gref_log_delete (value.Handle, ctype, tname, tid, from, 1);
+			}
 
 			base.DeleteGlobalReference (ref value);
 		}
@@ -220,25 +222,27 @@ public override JniObjectReference CreateWeakGlobalReference (JniObjectReference
 		{
 			var r = base.CreateWeakGlobalReference (value);
 
-			var log		= Logger.LogGlobalRef;
-			var ctype	= log ? GetObjectRefType (value.Type) : (byte) '*';
-			var ntype	= log ? GetObjectRefType (r.Type) : (byte) '*';
-			var tname = log ? Thread.CurrentThread.Name : null;
-			var tid   = log ? Thread.CurrentThread.ManagedThreadId : 0;
-			var from  = log ? new StringBuilder (new StackTrace (true).ToString ()) : null;
-			RuntimeNativeMethods._monodroid_weak_gref_new (value.Handle, ctype, r.Handle, ntype, tname, tid, from, 1);
+			if (Logger.LogGlobalRef) {
+				var ctype = GetObjectRefType (value.Type);
+				var ntype = GetObjectRefType (r.Type);
+				var tname = Thread.CurrentThread.Name;
+				var tid   = Thread.CurrentThread.ManagedThreadId;
+				var from  = new StringBuilder (new StackTrace (true).ToString ());
+				RuntimeNativeMethods._monodroid_weak_gref_new (value.Handle, ctype, r.Handle, ntype, tname, tid, from, 1);
+			}
 
 			return r;
 		}
 
 		public override void DeleteWeakGlobalReference (ref JniObjectReference value)
 		{
-			var log		= Logger.LogGlobalRef;
-			var ctype	= log ? GetObjectRefType (value.Type) : (byte) '*';
-			var tname = log ? Thread.CurrentThread.Name : null;
-			var tid   = log ? Thread.CurrentThread.ManagedThreadId : 0;
-			var from  = log ? new StringBuilder (new StackTrace (true).ToString ()) : null;
-			RuntimeNativeMethods._monodroid_weak_gref_delete (value.Handle, ctype, tname, tid, from, 1);
+			if (Logger.LogGlobalRef) {
+				var ctype = GetObjectRefType (value.Type);
+				var tname = Thread.CurrentThread.Name;
+				var tid   = Thread.CurrentThread.ManagedThreadId;
+				var from  = new StringBuilder (new StackTrace (true).ToString ());
+				RuntimeNativeMethods._monodroid_weak_gref_delete (value.Handle, ctype, tname, tid, from, 1);
+			}
 
 			base.DeleteWeakGlobalReference (ref value);
 		}