Imported Upstream version 4.3.2.467

Former-commit-id: 9c2cb47f45fa221e661ab616387c9cda183f283d

mcs/class/System.Threading.Tasks.Dataflow/CoreFxSources/Internal/Padding.cs

@@ -0,0 +1,37 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// Padding.cs
+//
+//
+// Helper structs for padding over CPU cache lines to avoid false sharing.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Runtime.InteropServices;
+
+namespace System.Threading.Tasks.Dataflow.Internal
+{
+    /// <summary>A placeholder class for common padding constants and eventually routines.</summary>
+    internal static class Padding
+    {
+        /// <summary>A size greater than or equal to the size of the most common CPU cache lines.</summary>
+        internal const int CACHE_LINE_SIZE = 128;
+    }
+
+    /// <summary>Padding structure used to minimize false sharing in SingleProducerSingleConsumerQueue{T}.</summary>
+    [StructLayout(LayoutKind.Explicit, Size = Padding.CACHE_LINE_SIZE - sizeof(Int32))] // Based on common case of 64-byte cache lines
+    internal struct PaddingForInt32
+    {
+    }
+
+    /// <summary>Value type that contains single Int64 value padded on both sides.</summary>
+    [StructLayout(LayoutKind.Explicit, Size = 2 * Padding.CACHE_LINE_SIZE)]
+    internal struct PaddedInt64
+    {
+        [FieldOffset(Padding.CACHE_LINE_SIZE)]
+        internal Int64 Value;
+    }
+}