Support for Python 3.15 `profiling.sampling`?

[rh-sp]

Python 3.15, currently in alpha, is planned to include a new built-in sampling profiler. The What's new page, perhaps misleadingly, attributes it to PEP 799, but the PEP itself doesn't actually describe the profiler, just suggests a new naming scheme for profilers / deprecation of old profile.

The profiling.sampling profiler contains an option to output "collapsed stack traces for flamegraphs." It would be fantastic if this format was supported by Speedscope.

• If it is a common format that is already supported, the new profiler could be added to the list of supported profilers in the README.
• Otherwise, maybe this new format could be added to Speedscope as a new feature.
• If neither, maybe one of the existing Python profilers exporting Speedscope compatible data could use profiling.sampling as a new backend.

What is the best approach here?

[jlfwong]

Hi! I'm open to any of these options.

Re: "maybe this new format could be added to Speedscope as a new feature.", I'm fine with accept a PR that does that provided that identifying a file is in the given format is efficient. Take a look at the import detection code to see what I mean

[rh-sp]

Here is an example:

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Speedscope imports it as collapsed stack format (BGFlameGraph). Looks like it doesn't interpret the tid as a thread ID though. Seems like a nonstandard addition. Not sure if multiprocessing is currently supported, at least I can't see process handling in the export code.

[rh-sp]

That said, profiling.sampling now also has a --flamegraph export option which renders an interactive HTML flamegraph including stuff such as code snippets from the sampled trace which isn't possible from the --collapsed output alone. However, this export does not support left heavy or sandwich views. So it can't do everything Speedscope can, but can do some things that Speedscope wouldn't be able to do with just the data from --collapsed. Not sure if it makes sense to invest time into supporting the tid syntax.

What's more interesting to me is the question of multiprocessing support, which py-spy does very nicely, but profiling.sampling appears to be lacking. So maybe the best way would be to approach py-spy about potentially using profiling.sampling as a backend.