[NativeAOT] Add sampling profiler

[filipnavara]

Presumably this is pretty useless since we don't do the rundown to get readable method names... but since I already have it laying around, anyone can think of a use for this?

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[MichalStrehovsky]

@LakshanF do you think we'd be able to implement the rest?

If there is a rundown for this, we do have names of methods available in stack trace metadata. If the rundown can run managed code, we could get it there. Maybe. Depending on what actually involves the rundown.

[filipnavara]

I only tried to run it with dotnet-trace and conversion to Speedscope format, which was quite useless, since you could see the stack traces but instead of method names there was just "?!?". I wonder if PerfView could perhaps show the addresses or correlate that to image base addresses. That would be already good enough for tools that can perform native symbolication (eg. Sentry).

Stack trace metadata sound like an interesting thing to try...

[LakshanF]

There is a work item in the diagnostic repo to lookup type information for native AOT GCDump, which could be expanded to include method information as well.

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Draft Pull Request was automatically closed for 30 days of inactivity. Please let us know if you'd like to reopen it.

[MichalStrehovsky]

This is useful on its own - without this, dotnet-gcdump will just hang at "Flushing the type table".

[MichalStrehovsky]

Thank you!

[Copilot]

Pull Request Overview

This PR introduces a basic sampling profiler for NativeAOT by adding helper methods and integrating stack walking logic.

• Added a new GetTransitionFrameForSampling method in thread.h
• Extended the sampling event capture logic in ep-rt-aot.cpp
• Introduced a GetControlPC method in StackFrameIterator.h

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/coreclr/nativeaot/Runtime/thread.h	Added a helper method to support sampling profiler functionality
src/coreclr/nativeaot/Runtime/eventpipe/ep-rt-aot.cpp	Integrated sampling profiler logic to capture stack frames and emit events
src/coreclr/nativeaot/Runtime/StackFrameIterator.h	Exposed the control PC via a new method for use by the profiler

Comments suppressed due to low confidence (3)

src/coreclr/nativeaot/Runtime/thread.h:323

• Consider adding a brief comment to clarify the purpose and usage of GetTransitionFrameForSampling for future maintainability.

PInvokeTransitionFrame* GetTransitionFrameForSampling() { return GetTransitionFrame(); }

src/coreclr/nativeaot/Runtime/eventpipe/ep-rt-aot.cpp:113

• [nitpick] Clarify or document in a tracking issue whether the differentiation between managed and external code will be addressed later to improve future code maintainability.

            // TODO: We can actually detect whether we are in managed or external code but does it matter?!

src/coreclr/nativeaot/Runtime/StackFrameIterator.h:58

• Consider adding a comment to describe the role of GetControlPC in the sampling process to aid future maintainers.

PTR_VOID         GetControlPC() { return m_ControlPC; }

[MichalStrehovsky]

/azp run runtime-nativeaot-outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[MichalStrehovsky]

/ba-g the arm32 build break was fixed and the rest are known