Windows-Containers Can't just use "all available" hardware resources

Describe the bug According to the Docker documentation: https://docs.docker.com/config/containers/resource_constraints/ there should be by default no resource constraints. However, if I do not specify how much RAM and how many CPUs to use, it always just uses 1 core and 2 logical processors and 5GB of RAM. Even if I specifically say --cpus 0 when creating the container, which should use all available cores, it still restricts it to the default. Right now I have no idea how to tell the container to use all available resources without specifying all resources. If this is a bug in Docker for Windows and I need to report it there, please tell me.

To Reproduce Steps to reproduce the behavior:

Make a docker image from mcr.microsoft.com/windows/servercore:ltsc2022
docker build -t myimage -m 4GB .
docker run --name Windows -it myimage
In the container execute wmic cpu get NumberOfCores,NumberOfLogicalProcessors
If you have more than one core, it will still only show one

Expected behavior The container should use all available resources

Configuration:

Edition: Windows 11
Base Image being used: Windows Server Core
Container engine: docker
Container Engine version: 24

Additional context Add any other context about the problem here.

Oct 19 '23 08:10 Outtay

🔖 ADO #47827961

Nov 23 '23 00:11 ntrappe-msft

Hi @Outtay,

There are two kind of Windows Containers:

Process Isolated Containers
Hyper-V Isolated Containers.

For Hyper-V isolated containers, we can have WCOW and LCOW. WCOW means Windows Container on Windows, LCOW means Linux Container on Windows, docker client installation called WSL.

For process isolated containers, we can't assign the CPU and memory to a container like we can do for a Hyper-V isolated container, but we can limit how much CPU and memory a container can consume. For example,

docker run -it -m 4096M ---cpu-percent=20 --name mytest windows cmd.exe

This command will create a container that can only consume up to 4GB physical memories and 20 percent of the total available CPU. As the CPU core concerns, it still can see all the cores inside the container, but it can only consume up to 20% of the CPU resources.

For Hyper-V isolated containers, it will assigned the CPU and memory resources at the container startup time, just like a Hyper-V VM scenario. For example:

docker run -it -m 4096M --cpu-count=8 --name mytest --isolation=hyperv windows cmd.exe

With this command, the docker will create a container with 4GB and 8 cores assigned to the container, event the container host has 12 cores. BTW, the default Hyper-V container CPU core is 2 and memory is 1GB.

Please let me know if you have any questions.

Jan 04 '24 00:01 Howard-Haiyang-Hao

Hi @Howard-Haiyang-Hao,

thanks for the response.

Under Linux and according to the general Docker documentation there shouldn't be any resource constraints by default. I also couldn't find any documentation stating that Windows works differently in that regard, as in the case of using Hyper-V Isolated Containers and specifying no resources, not all resources can be used by the container. However, I was under the impression that I had the same problem when using Process Isolated containers. That seemed to have been an error on my part. When I tested it right now all resources were available when specifying none.

My specific use case is setting up different physical hardware for running pipelines and building and testing an application in a docker container. Since they should not be doing anything else I want them to use all available resources. However, they're all different machines and therefore have different parameters, which means that specifying the correct parameters is a minor source of error. An unnecessary one, as I should not need to specify it.

Since using process isolation works as I would expect it, I can try using that and hoping that it works. However, with Hyper-V isolation mode this should in my opinion be changed to work consistent with other modes or would need to be documented as an exception (if it isn't already. I couldn't find that though). As a workaround it would have also been nice, if there was an option that just results in everything being used (like entering 0 or INT_MAX for cpu-count or 100 for cpu-percent would then result in the maximum amount of cores being assigned and used)

Jan 04 '24 15:01 Outtay