`_remote_debugging`: `RemoteUnwinder(..., jit=True)`

Feature or enhancement

Proposal:

:)

The idea here is to expose JIT internals a bit more in the Tachyon profiler.

The questions that could be answered trivially:

• Is JIT actually used? How often?
• Which executor is hot?
• What change made the largest difference (diff_flamegraph), in terms of % spent in JIT? Per line?

A bit harder:

• Which UOPs actually eat time?
• Which stensils are good?
• What guards or deopts are bad?
• What is the trace shape?

The very minimal change that I'm thinking about here is just adding --jit flag (active for --jsonl and maybe for --live but it's a catnip), and adding JitInfo to ThreadInfo.

That's how it could look:

JitInfo(
  executor_id,
  flags
)

This will requires extending debug offsets, obviously.

We could potentially expose native_pc, native_offset, uop_index, exit_index etc. The question would be how to expose metadata for it without balooning JitInfo, and how far we can get without blocking and native unwinding. :)

I'm pretty much open to any other ideas.

There will be definitely some performance impact (more VM reads), but hidden behind the --enable-experimental-jit flag should be bearable, and we could be more playful, going back and forth.

If you think it makes sense, I'd be willing to take a shot, but this will take multiple PRs.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Bắt đầu bằng cách lần theo _remote_debugging, RemoteUnwinder(..., jit=True) và luồng ThreadInfo hiện có. So sánh hành vi --jit được đề xuất cho --jsonl và có thể là --live, sau đó kiểm tra cách các offset gỡ lỗi được xử lý. Công việc được xem là hoàn tất khi đã xác định rõ phạm vi để cung cấp JitInfo và metadata của nó phía sau --enable-experimental-jit, đồng thời cân nhắc ảnh hưởng đến hiệu năng.