JIT pre-compile for .NET core

I want to have some better performance for the code I write in C# core using jit pre-compile abilities.

I have seen an issue that is called JIT, and explanation that the windows-system make small compilations that are called JIT (just in time), and that I can do some pre-compilation for the executable/dll I make.

The link: Youtube jit tutorial explains in details how doing a pre-compilation for JIT, by using command ngen install ...

Can I do pre-jit on .NET core? (.NET core is running by the command: dotnet . There is never an executable file)? Also can I do pre-jit for C# core that is running on dockers for linux (the pre-jit inside the docker)

How can I check the JIT actually? (in performance monitor I cannot see the dll I an running by command: dotnet mydll.dll)

Can I run for .NET core the following code?:

ngen install

Need some examples, please.

I have heard about crossgen, and see the link

stackoverflow crossgen

I didn't understand what is the appropoiate checklist to pre-build to my code.

I add see a new folder on: C:\Users\.nuget\packages\runtime.osx.10.10-x64.microsoft.netcore.runtime.coreclr\1.1.10

but it seems not relevant for windows platform.

As the link on the comment: https://github.com/dotnet/coreclr/blob/master/Documentation/building/crossgen.md that brian sent, I tried something like this:

C:\Users\my user name\.nuget\packages\runtime.win-x64.microsoft.netcore.runtime.coreclr\2.0.8\Tools\crossgen.exe /JITPath C:\Windows\Microsoft.NET\Framework64\v4.0.30319\clrjit.dll /Platform_Assemblies_Paths "C:\Users\my user name\source\repos\test\testCore\bin\Release\netcoreapp2.1" C:\Users\my user name\source\repos\test\testCore\bin\Release\netcoreapp2.1\testCore.dll

I got the message:

The system cannot find the file specified. (Exception from HRESULT: 0x80070002) ... Error: file "C:\Users\my user name \source\repos\test\testCore\bin\Release\netcoreapp2.1\testCore.dll" or one of its dependencies was not found

Thanks.