From 77b9fd82a7ef68f894a25ef79787ec3616b48e99 Mon Sep 17 00:00:00 2001
From: Daniel Weber <dw@exram.de>
Date: Fri, 22 Jun 2018 17:45:23 +0200
Subject: [PATCH 1/2] Add Benchmark for Switch.

---
 .../Benchmarks.System.Reactive/Program.cs     |  3 ++-
 .../SwitchBenchmark.cs                        | 25 +++++++++++++++++++
 .../ZipBenchmark.cs                           |  2 +-
 3 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/SwitchBenchmark.cs

diff --git a/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/Program.cs b/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/Program.cs
index 3776f8cad8..ad89ca78d4 100644
--- a/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/Program.cs
+++ b/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/Program.cs
@@ -13,7 +13,8 @@ static void Main()
         {
             var switcher = new BenchmarkSwitcher(new[] {
                 typeof(ZipBenchmark),
-                typeof(CombineLatestBenchmark)
+                typeof(CombineLatestBenchmark),
+                typeof(SwitchBenchmark)
             });
 
             switcher.Run();
diff --git a/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/SwitchBenchmark.cs b/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/SwitchBenchmark.cs
new file mode 100644
index 0000000000..17b94c1f4d
--- /dev/null
+++ b/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/SwitchBenchmark.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information.
+
+using System.Reactive.Linq;
+using BenchmarkDotNet.Attributes;
+using System.Reactive.Threading.Tasks;
+using System.Threading.Tasks;
+
+namespace Benchmarks.System.Reactive
+{
+    [MemoryDiagnoser]
+    public class SwitchBenchmark
+    {
+        [Benchmark]
+        public async Task Switch_10000_Sources()
+        {
+            await Observable
+                .Range(1, 10000)
+                .Select(x => Observable.Return(x))
+                .Switch()
+                .ToTask();
+        }
+    }
+}
diff --git a/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/ZipBenchmark.cs b/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/ZipBenchmark.cs
index 108264c247..53720dd4b5 100644
--- a/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/ZipBenchmark.cs
+++ b/Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/ZipBenchmark.cs
@@ -77,7 +77,7 @@ public void Zip_AllCompleted7()
         {
             _zipTest.Zip_AllCompleted7();
         }
-        
+
         [Benchmark]
         public void Zip_AllCompleted8()
         {

From 3658aae7da34aef22504496888fe91cdfa92b635 Mon Sep 17 00:00:00 2001
From: Daniel Weber <dw@exram.de>
Date: Tue, 19 Jun 2018 16:56:06 +0200
Subject: [PATCH 2/2] Save an allocation during inner observer creation in
 Switch.

---
 .../System.Reactive/Linq/Observable/Switch.cs | 23 +++++++++----------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/Rx.NET/Source/src/System.Reactive/Linq/Observable/Switch.cs b/Rx.NET/Source/src/System.Reactive/Linq/Observable/Switch.cs
index 139f4ae388..45642046dc 100644
--- a/Rx.NET/Source/src/System.Reactive/Linq/Observable/Switch.cs
+++ b/Rx.NET/Source/src/System.Reactive/Linq/Observable/Switch.cs
@@ -50,9 +50,10 @@ public override void OnNext(IObservable<TSource> value)
                     _hasLatest = true;
                 }
 
-                var d = new SingleAssignmentDisposable();
-                Disposable.TrySetSerial(ref _innerSerialDisposable, d);
-                d.Disposable = value.SubscribeSafe(new InnerObserver(this, id, d));
+                var innerObserver = new InnerObserver(this, id);
+
+                Disposable.TrySetSerial(ref _innerSerialDisposable, innerObserver);
+                innerObserver.SetResource(value.SubscribeSafe(innerObserver));
             }
 
             public override void OnError(Exception error)
@@ -75,20 +76,18 @@ public override void OnCompleted()
                 }
             }
 
-            private sealed class InnerObserver : IObserver<TSource>
+            private sealed class InnerObserver : SafeObserver<TSource>
             {
                 private readonly _ _parent;
                 private readonly ulong _id;
-                private readonly IDisposable _self;
 
-                public InnerObserver(_ parent, ulong id, IDisposable self)
+                public InnerObserver(_ parent, ulong id)
                 {
                     _parent = parent;
                     _id = id;
-                    _self = self;
                 }
 
-                public void OnNext(TSource value)
+                public override void OnNext(TSource value)
                 {
                     lock (_parent._gate)
                     {
@@ -99,11 +98,11 @@ public void OnNext(TSource value)
                     }
                 }
 
-                public void OnError(Exception error)
+                public override void OnError(Exception error)
                 {
                     lock (_parent._gate)
                     {
-                        _self.Dispose();
+                        Dispose();
 
                         if (_parent._latest == _id)
                         {
@@ -112,11 +111,11 @@ public void OnError(Exception error)
                     }
                 }
 
-                public void OnCompleted()
+                public override void OnCompleted()
                 {
                     lock (_parent._gate)
                     {
-                        _self.Dispose();
+                        Dispose();
 
                         if (_parent._latest == _id)
                         {