Re: [PATCH] perf python: Accept events larger than union perf_event

[sashiko-bot@kernel.org]

> Samples recorded with --call-graph dwarf carry a copy of the user stack
> and are larger than union perf_event, so session.process_events()
> fails on the first one:
> 
>   $ perf record --call-graph dwarf -- ./workload
>   $ python3 tools/perf/python/stackcollapse.py
>   ...
>   TypeError: Unexpected event size: 4168 < 8424
> 
> This makes all the standalone scripts unusable on such recordings.
> 
> pyrf_event__new() rejects events larger than union perf_event, which
> guarded the copy into the union that pyrf_event used to embed. Since
> commit 2c672ffdad4b ("perf python: Lazily copy events and samples from
> process_events") the event is borrowed, or copied to a buffer of
> header.size bytes when a callback keeps it, so nothing depends on the
> event fitting in the union any more. Remove the check.
> 
> With this, stackcollapse.py and flamegraph.py process a DWARF recording
> of a two-thread workload, with the same per-symbol sample counts as
> perf script, also when the callback keeps the events after returning.
> 
> Assisted-by: LLM
> Signed-off-by: Lalit Maganti <lalitmaganti@gmail.com>

Sashiko has reviewed this patch and found no issues.

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