Ready2Run images are still loaded when COR_PRF_DISABLE_ALL_NGEN_IMAGES is set

[davmason]

From the profiler's point of view, it does not know about the differences between R2R and NGEN. There is a profiler flag to set COR_PRF_DISABLE_ALL_NGEN_IMAGES, to ensure that no pre-generated code is loaded.

However, this flag does not prevent the loading of R2R images. This is an issue for the profiler because pre-generated code cannot be instrumented, such as enter/leave callbacks, does not have jit events, etc.

I wrote a sample profiler and tested it without COR_PRF_DISABLE_ALL_NGEN_IMAGES, with it, and without it plus COMPLUS_ReadyToRun=0. Here are the results. Note that "loaded as NGEN" just means loaded as a pre-compiled library, they are all R2R except for System.Private.CoreLib

****************** Testing with profiler allowing NGEN **********************
Profiler initialized.
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Private.CoreLib.ni.dll" loaded as NGEN
Module "D:\Ready2RunProfilerRepro\Ready2RunTest.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Runtime.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\mscorlib.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Console.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.IO.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Threading.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.IO.FileSystem.Primitives.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Text.Encoding.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Text.Encoding.Extensions.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Threading.Tasks.dll" loaded as NGEN
Hello World!


****************** Testing with profiler COR_PRF_DISABLE_ALL_NGEN_IMAGES set **********************
Profiler forbidding NGEN
Profiler initialized.
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Private.CoreLib.ni.dll" loaded as IL
Module "D:\Ready2RunProfilerRepro\Ready2RunTest.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Runtime.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\mscorlib.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Console.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.IO.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Threading.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.IO.FileSystem.Primitives.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Text.Encoding.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Text.Encoding.Extensions.dll" loaded as NGEN
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Threading.Tasks.dll" loaded as NGEN
Hello World!


****************** Testing with COMPLUS_ReadyToRun=0 **********************
Profiler initialized.
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Private.CoreLib.ni.dll" loaded as NGEN
Module "D:\Ready2RunProfilerRepro\Ready2RunTest.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Runtime.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\mscorlib.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Console.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.IO.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Threading.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.IO.FileSystem.Primitives.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Text.Encoding.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Text.Encoding.Extensions.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Threading.Tasks.dll" loaded as IL
Module "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.1.2\System.Runtime.InteropServices.dll" loaded as IL
Hello World!

[davmason]

Fixed in dotnet/coreclr#13043

[mmayr-at]

I just ran into this issue with the latest .NET Core 2.0.0 Preview. I tried an ASP.NET Core application and was not able to instrument code into the Micrsoft.AspNetCore.Http.Abstractions.dll assembly. Then I found out that a this was a r2r image.

I see that this is planned for Milestone 2.1.0, but I would like to see this included in the 2.0.0 release. Otherwise we must use a workaround and set the ReadyToRun option for every process we would like to profile.

/CC @jkotas @noahfalk

[davmason]

@mmayr-at It is unfortunately too late for 2.0, it has already locked down.

For what it's worth, this fix means that when a profiler is attached and requests that NGEN images are not loaded, it is the same impact as setting COMPLUS_ReadyToRun=0. You don't gain anything with this fix, other than not having to set the extra environment variable.

[mmayr-at]

This is bad news for us, but thanks for that information. I know that the workaround is quite easy, but we have to deploy it to production/testing environments and have to consider it in everyday development tasks.

[jkotas]

@davmason We should include this fix in the first 2.0 servicing update (2.0.1).

[mmayr-at]

@jkotas This is definitely better than waiting for the 2.1.0 release, thx.

[danmoseley]

dotnet/coreclr#13349