gh-142374: Fix recursive function cumulative over-counting in sampling profiler #142378
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…ampling profiler The sampling profiler counted every frame occurrence in a stack for cumulative statistics. For recursive functions appearing N times in a stack, this meant counting N instead of 1, causing cumul% to exceed 100%. A function recursing 500 deep in every sample would show 50000% cumulative presence. The fix tracks seen locations per sample using a reused set, ensuring each unique (filename, lineno, funcname) is counted once per sample. This matches the expected semantics: cumul% represents the percentage of samples where a function appeared on the stack, not the sum of all frame occurrences.
kmk142789
approved these changes
Dec 7, 2025
kmk142789
previously approved these changes
Dec 7, 2025
pablogsal
commented
Dec 8, 2025
Co-authored-by: Stan Ulbrych <[email protected]>
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The sampling profiler counted every frame occurrence in a stack for
cumulative statistics. For recursive functions appearing N times in a stack,
this meant counting N instead of 1, causing cumul% to exceed 100%. A function
recursing 500 deep in every sample would show 50000% cumulative presence.
The fix tracks seen locations per sample using a reused set, ensuring each
unique (filename, lineno, funcname) is counted once per sample. This matches
the expected semantics: cumul% represents the percentage of samples where a
function appeared on the stack, not the sum of all frame occurrences.