From a62bfd7ee0d29cb817f6ce55fc41f67f62813b54 Mon Sep 17 00:00:00 2001
From: Stephen Toub <stoub@microsoft.com>
Date: Wed, 25 Nov 2020 15:39:25 -0500
Subject: [PATCH 1/3] Reduce allocation from OptionsCache's concurrent
 dictionary

This type is primarily used for getting and rarely mutated after startup; we don't need to pay for lots of lock objects to optimize for mutation.
---
 src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs b/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs
index b4094fe54de20a..e18b5a75b9bb88 100644
--- a/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs
+++ b/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs
@@ -15,7 +15,7 @@ public class OptionsCache<[DynamicallyAccessedMembers(Options.DynamicallyAccesse
         IOptionsMonitorCache<TOptions>
         where TOptions : class
     {
-        private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(StringComparer.Ordinal);
+        private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(concurrencyLevel: 1, capacity: 31, StringComparer.Ordinal);
 
         /// <summary>
         /// Clears all options instances from the cache.

From dd0b9961b711bd78866231198dc67b447c60e3cc Mon Sep 17 00:00:00 2001
From: Stephen Toub <stoub@microsoft.com>
Date: Wed, 25 Nov 2020 15:50:37 -0500
Subject: [PATCH 2/3] Avoid closure/delegate allocations in
 `OptionsManager<T>.Value`

---
 .../src/OptionsCache.cs                       | 18 ++++++++++++++++++
 .../src/OptionsManager.cs                     | 19 ++++++++++---------
 2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs b/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs
index e18b5a75b9bb88..55f97a44202c9a 100644
--- a/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs
+++ b/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs
@@ -38,6 +38,24 @@ public virtual TOptions GetOrAdd(string name, Func<TOptions> createOptions)
             return _cache.GetOrAdd(name, new Lazy<TOptions>(createOptions)).Value;
         }
 
+        /// <summary>
+        /// Gets a named options instance, if available.
+        /// </summary>
+        /// <param name="name">The name of the options instance.</param>
+        /// <param name="options">The options instance.</param>
+        /// <returns>true if the options were retrieved; otherwise, false.</returns>
+        internal bool TryGetValue(string name, out TOptions options)
+        {
+            if (_cache.TryGetValue(name ?? Options.DefaultName, out Lazy<TOptions> lazy))
+            {
+                options = lazy.Value;
+                return true;
+            }
+
+            options = default;
+            return false;
+        }
+
         /// <summary>
         /// Tries to adds a new option to the cache, will return false if the name already exists.
         /// </summary>
diff --git a/src/libraries/Microsoft.Extensions.Options/src/OptionsManager.cs b/src/libraries/Microsoft.Extensions.Options/src/OptionsManager.cs
index 71b5a134f35139..83fc0ecc8e9050 100644
--- a/src/libraries/Microsoft.Extensions.Options/src/OptionsManager.cs
+++ b/src/libraries/Microsoft.Extensions.Options/src/OptionsManager.cs
@@ -29,13 +29,7 @@ public OptionsManager(IOptionsFactory<TOptions> factory)
         /// <summary>
         /// The default configured <typeparamref name="TOptions"/> instance, equivalent to Get(Options.DefaultName).
         /// </summary>
-        public TOptions Value
-        {
-            get
-            {
-                return Get(Options.DefaultName);
-            }
-        }
+        public TOptions Value => Get(Options.DefaultName);
 
         /// <summary>
         /// Returns a configured <typeparamref name="TOptions"/> instance with the given <paramref name="name"/>.
@@ -44,8 +38,15 @@ public virtual TOptions Get(string name)
         {
             name = name ?? Options.DefaultName;
 
-            // Store the options in our instance cache
-            return _cache.GetOrAdd(name, () => _factory.Create(name));
+            if (!_cache.TryGetValue(name, out TOptions options))
+            {
+                // Store the options in our instance cache. Avoid closure on fast path by storing state into scoped locals.
+                IOptionsFactory<TOptions> localFactory = _factory;
+                string localName = name;
+                options = _cache.GetOrAdd(name, () => localFactory.Create(localName));
+            }
+
+            return options;
         }
     }
 }

From fb01382e3a7c49c4917b94e1087302f3a0af82bb Mon Sep 17 00:00:00 2001
From: Stephen Toub <stoub@microsoft.com>
Date: Wed, 25 Nov 2020 16:16:49 -0500
Subject: [PATCH 3/3] Update
 src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs

Co-authored-by: David Fowler <davidfowl@gmail.com>
---
 src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs b/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs
index 55f97a44202c9a..29c38881eec080 100644
--- a/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs
+++ b/src/libraries/Microsoft.Extensions.Options/src/OptionsCache.cs
@@ -15,7 +15,7 @@ public class OptionsCache<[DynamicallyAccessedMembers(Options.DynamicallyAccesse
         IOptionsMonitorCache<TOptions>
         where TOptions : class
     {
-        private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(concurrencyLevel: 1, capacity: 31, StringComparer.Ordinal);
+        private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(concurrencyLevel: 1, capacity: 31, StringComparer.Ordinal); // 31 == default capacity
 
         /// <summary>
         /// Clears all options instances from the cache.