From d32314361ce35c20b846e402f898f920851e59db Mon Sep 17 00:00:00 2001
From: Alex Covington <acovingt@amd.com>
Date: Wed, 4 Nov 2020 13:29:07 -0800
Subject: [PATCH 1/3] Allow threads to sleep when ConcurrentQueue has many
 enqueuers/dequeuers.

---
 .../Collections/Concurrent/ConcurrentQueueSegment.cs     | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs b/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs
index 1cd82352ae1754..af7c170464f4fe 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs
@@ -37,6 +37,9 @@ internal sealed class ConcurrentQueueSegment<T>
         internal ConcurrentQueueSegment<T>? _nextSegment; // SOS's ThreadPool command depends on this name
 #pragma warning restore 0649
 
+        /// <summary>Threshold to spin before allowing threads to sleep when there is contention.</summary>
+        internal const int _sleep1Threshold = 8;
+
         /// <summary>Creates the segment.</summary>
         /// <param name="boundedLength">
         /// The maximum number of elements the segment can contain.  Must be a power of 2.
@@ -183,7 +186,7 @@ public bool TryDequeue([MaybeNullWhen(false)] out T item)
                 }
 
                 // Lost a race. Spin a bit, then try again.
-                spinner.SpinOnce(sleep1Threshold: -1);
+                spinner.SpinOnce(sleep1Threshold: _sleep1Threshold);
             }
         }
 
@@ -244,7 +247,7 @@ public bool TryPeek([MaybeNullWhen(false)] out T result, bool resultUsed)
                 }
 
                 // Lost a race. Spin a bit, then try again.
-                spinner.SpinOnce(sleep1Threshold: -1);
+                spinner.SpinOnce(sleep1Threshold: _sleep1Threshold);
             }
         }
 
@@ -301,7 +304,7 @@ public bool TryEnqueue(T item)
                 }
 
                 // Lost a race. Spin a bit, then try again.
-                spinner.SpinOnce(sleep1Threshold: -1);
+                spinner.SpinOnce(sleep1Threshold: _sleep1Threshold);
             }
         }
 

From 14fb73d88931e583164f0a5252980f746292b317 Mon Sep 17 00:00:00 2001
From: Alex Covington <68252706+alexcovington@users.noreply.github.com>
Date: Thu, 5 Nov 2020 09:52:01 -0800
Subject: [PATCH 2/3] Update
 src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs

Co-authored-by: Stephen Toub <stoub@microsoft.com>
---
 .../src/System/Collections/Concurrent/ConcurrentQueueSegment.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs b/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs
index af7c170464f4fe..8ecc01432fa94a 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs
@@ -186,7 +186,7 @@ public bool TryDequeue([MaybeNullWhen(false)] out T item)
                 }
 
                 // Lost a race. Spin a bit, then try again.
-                spinner.SpinOnce(sleep1Threshold: _sleep1Threshold);
+                spinner.SpinOnce(Sleep1Threshold);
             }
         }
 

From 729d6468e97eeecdf752290ed47ac85f518cbdc1 Mon Sep 17 00:00:00 2001
From: Alex Covington <68252706+alexcovington@users.noreply.github.com>
Date: Thu, 5 Nov 2020 09:52:43 -0800
Subject: [PATCH 3/3] Apply suggestions from code review

Co-authored-by: Stephen Toub <stoub@microsoft.com>
---
 .../System/Collections/Concurrent/ConcurrentQueueSegment.cs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs b/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs
index 8ecc01432fa94a..e238c5b8d834c5 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueueSegment.cs
@@ -38,7 +38,7 @@ internal sealed class ConcurrentQueueSegment<T>
 #pragma warning restore 0649
 
         /// <summary>Threshold to spin before allowing threads to sleep when there is contention.</summary>
-        internal const int _sleep1Threshold = 8;
+        private const int Sleep1Threshold = 8;
 
         /// <summary>Creates the segment.</summary>
         /// <param name="boundedLength">
@@ -247,7 +247,7 @@ public bool TryPeek([MaybeNullWhen(false)] out T result, bool resultUsed)
                 }
 
                 // Lost a race. Spin a bit, then try again.
-                spinner.SpinOnce(sleep1Threshold: _sleep1Threshold);
+                spinner.SpinOnce(Sleep1Threshold);
             }
         }
 
@@ -304,7 +304,7 @@ public bool TryEnqueue(T item)
                 }
 
                 // Lost a race. Spin a bit, then try again.
-                spinner.SpinOnce(sleep1Threshold: _sleep1Threshold);
+                spinner.SpinOnce(Sleep1Threshold);
             }
         }