diff --git a/build/dependencies.props b/build/dependencies.props
index 6e343231b3..68a0c2e10a 100644
--- a/build/dependencies.props
+++ b/build/dependencies.props
@@ -1,6 +1,7 @@
 <Project>
   <PropertyGroup>
     <AspNetCoreVersion>2.0.0-*</AspNetCoreVersion>
+    <SystemMemoryVersion>4.4.0-*</SystemMemoryVersion>
     <InternalAspNetCoreSdkVersion>2.1.0-*</InternalAspNetCoreSdkVersion>
     <LibUvVersion>1.10.0-*</LibUvVersion>
     <JsonNetVersion>9.0.1</JsonNetVersion>
diff --git a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameAdapter.cs b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameAdapter.cs
index 6659b83bf8..1418fb8b44 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameAdapter.cs
+++ b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameAdapter.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.System;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
diff --git a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameRequestHeaders.cs b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameRequestHeaders.cs
index fb543805cb..d1bfc945e3 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameRequestHeaders.cs
+++ b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameRequestHeaders.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
diff --git a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/HttpParser.cs b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/HttpParser.cs
index a9751e245c..3445dc2098 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/HttpParser.cs
+++ b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/HttpParser.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Runtime.CompilerServices;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.System;
diff --git a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/IHttpHeadersHandler.cs b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/IHttpHeadersHandler.cs
index a9ad79559a..2cf4789c22 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/IHttpHeadersHandler.cs
+++ b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/IHttpHeadersHandler.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.System;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
diff --git a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/IHttpRequestLineHandler.cs b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/IHttpRequestLineHandler.cs
index 05088aacc4..4cc1fe7478 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/IHttpRequestLineHandler.cs
+++ b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/IHttpRequestLineHandler.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.System;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
diff --git a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/PathNormalizer.cs b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/PathNormalizer.cs
index 645dd4629c..7372fcb71a 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/PathNormalizer.cs
+++ b/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/PathNormalizer.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Diagnostics;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.System;
 
diff --git a/src/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions.csproj b/src/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions.csproj
index 45adabecd7..cec4f50a65 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions.csproj
+++ b/src/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions.csproj
@@ -10,12 +10,15 @@
     <NoWarn>CS1570;CS1571;CS1572;CS1573;CS1574;CS1591;$(NoWarn)</NoWarn>
     <EnableApiCheck>false</EnableApiCheck>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <UseSystemMemory>false</UseSystemMemory>
     <DefineConstants>$(DefineConstants);KESTREL_BY_SOURCE</DefineConstants>
+    <DefineConstants Condition="'$(UseSystemMemory)' == 'true'">$(DefineConstants);SYSTEM_MEMORY</DefineConstants>
   </PropertyGroup>
 
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.Internal.CoreFxLab.Sources" Version="$(AspNetCoreVersion)" PrivateAssets="All" />
     <PackageReference Include="Microsoft.AspNetCore.Http.Features" Version="$(AspNetCoreVersion)" />
+    <PackageReference Condition="'$(UseSystemMemory)' == 'true'" Include="System.Memory" Version="$(SystemMemoryVersion)" />
   </ItemGroup>
 
 </Project>
diff --git a/test/Microsoft.AspNetCore.Server.Kestrel.Core.Tests/HttpParserTests.cs b/test/Microsoft.AspNetCore.Server.Kestrel.Core.Tests/HttpParserTests.cs
index c98818f506..ee53a68d7f 100644
--- a/test/Microsoft.AspNetCore.Server.Kestrel.Core.Tests/HttpParserTests.cs
+++ b/test/Microsoft.AspNetCore.Server.Kestrel.Core.Tests/HttpParserTests.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
diff --git a/test/Microsoft.AspNetCore.Server.Kestrel.Core.Tests/TestHelpers/AssertExtensions.cs b/test/Microsoft.AspNetCore.Server.Kestrel.Core.Tests/TestHelpers/AssertExtensions.cs
index d6ddbee945..1ca99370e5 100644
--- a/test/Microsoft.AspNetCore.Server.Kestrel.Core.Tests/TestHelpers/AssertExtensions.cs
+++ b/test/Microsoft.AspNetCore.Server.Kestrel.Core.Tests/TestHelpers/AssertExtensions.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.System;
 using Xunit.Sdk;
 
diff --git a/test/Microsoft.AspNetCore.Server.Kestrel.Performance/KestrelHttpParserBenchmark.cs b/test/Microsoft.AspNetCore.Server.Kestrel.Performance/KestrelHttpParserBenchmark.cs
index 858c973400..30238b3223 100644
--- a/test/Microsoft.AspNetCore.Server.Kestrel.Performance/KestrelHttpParserBenchmark.cs
+++ b/test/Microsoft.AspNetCore.Server.Kestrel.Performance/KestrelHttpParserBenchmark.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using BenchmarkDotNet.Attributes;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.System;
diff --git a/test/Microsoft.AspNetCore.Server.Kestrel.Performance/Mocks/NullParser.cs b/test/Microsoft.AspNetCore.Server.Kestrel.Performance/Mocks/NullParser.cs
index 54d71cf795..1484b2af44 100644
--- a/test/Microsoft.AspNetCore.Server.Kestrel.Performance/Mocks/NullParser.cs
+++ b/test/Microsoft.AspNetCore.Server.Kestrel.Performance/Mocks/NullParser.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Text;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.System;