Run server GC OOP with reduced process priority

src/Workspaces/Remote/ServiceHub/Services/Host/ProcessExtensions.cs

@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.ComponentModel;
+using System.Diagnostics;
+
+namespace Microsoft.CodeAnalysis.Remote
+{
+    internal static class ProcessExtensions
+    {
+        private static bool s_settingPrioritySupported = true;
+
+        public static bool TrySetPriorityClass(this Process process, ProcessPriorityClass priorityClass)
+        {
+            if (!s_settingPrioritySupported)
+            {
+                return false;
+            }
+
+            try
+            {
+                process.PriorityClass = priorityClass;
+                return true;
+            }
+            catch (Exception e) when (e is PlatformNotSupportedException or Win32Exception)
+            {
+                // the runtime does not support changing process priority
+                s_settingPrioritySupported = false;
+
+                return false;
+            }
+        }
+    }
+}

src/Workspaces/Remote/ServiceHub/Services/Host/RemoteHostService.cs

@@ -10,6 +10,7 @@
 using System.Globalization;
 using System.IO;
 using System.Linq;
+using System.Runtime;
 using System.Runtime.InteropServices;
 using System.Text;
 using System.Threading;
@@ -51,6 +52,14 @@ internal partial class RemoteHostService : ServiceBase, IRemoteHostService, IAss
 
         static RemoteHostService()
         {
+            if (GCSettings.IsServerGC)
+            {
+                // Server GC runs processor-affinitized threads with high priority. To avoid interfering with other
+                // applications while still allowing efficient out-of-process execution, slightly reduce the process
+                // priority when using server GC.
+                Process.GetCurrentProcess().TrySetPriorityClass(ProcessPriorityClass.BelowNormal);
+            }
+
             // this is the very first service which will be called from client (VS)
             // we set up logger here
             RoslynLogger.SetLogger(new EtwLogger(s_logChecker));