Support for Windows Server, version 2004

[mthalman]

Support for Windows Server, version 2004

With the release of Windows Server, version 2004 on May 27, 2020, .NET Framework Docker images have been published for Windows Server Core, version 2004.

Details

• dotnet-framework-docker#560

.NET Framework tags containing the substring windowsservercore-2004 are now available. You can find the full set of tags on Docker Hub.

.NET Framework multi-arch tags, such as 4.8, have been updated to use windowsservercore-2004 images if your host is Windows Server, version 2004.

Impacted Repos

• dotnet/framework/sdk: .NET Framework SDK
• dotnet/framework/aspnet: ASP.NET Runtime
• dotnet/framework/wcf: Windows Communication Foundation
• dotnet/framework/runtime: .NET Framework Runtime
• dotnet/framework/samples: .NET Framework Samples

Known Issues

Performance Issue with Windows Server Core Containers

We recently discovered a performance issue with .NET Framework running in Windows Server, version 2004 container images. This issue is noticeable compared to using Windows Server, version 1909 images. We have improved .NET Framework performance in containers significantly, such that compared to Windows Server, version 1903 images and earlier, the performance issue is not expected to be noticeable.

See Windows Server known issues.

The performance issue has been observed as significant CPU cycles early in the life of a container process, either at startup or a short time later. This can cause startup to be slower or cause the process to be slower for a short period after that. We have observed normal behavior after the short drop in performance.

We are actively researching this performance issue, and collaborating with the Windows Server team.

See the following links that are tracking these issues:

• WCOW delta layers can have incorrect directory modification timestamps hcsshim#830
• Slow Windows container start time when using servercore image moby/moby#41066
• Slow Windows container start time when using servercore image containerd/containerd#4301

32-bit Application Performance

Significant work was done with the version 2004 release to reduce the image size. This resulted in the base Windows Docker image having only a few key assemblies as being ngen-compiled.

The .NET Framework Docker image then needed to optimize for the most common .NET Framework and PowerShell scenarios by running ngen compilation on additional assemblies. This was done for 64-bit assemblies only.

In order to keep the image size down, 32-bit assemblies are no longer being ngen-compiled starting in version 2004 images. This means that any 32-bit .NET Framework applications will likely execute slower in version 2004 than in earlier versions of Windows Server. If you're experiencing performance issues with your 32-bit application, this can be mitigated by running 32-bit ngen within your own Dockerfile. When a file is ngen-compiled, it affects the entire graph that the file references in a recursive manner. For that reason, you only really need to ngen-compile the root assembly of your application. Here are some examples:

Console Application

RUN \Windows\Microsoft.NET\Framework\v4.0.30319\ngen install application.exe

Web Application

RUN \Windows\Microsoft.NET\Framework\v4.0.30319\ngen install website.dll

32-bit PowerShell

RUN \Windows\Microsoft.NET\Framework\v4.0.30319\ngen install "Microsoft.PowerShell.Utility.Activities, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"