gh-142374: Fix recursive function cumulative over-counting in sampling profiler#142378
Merged
pablogsal merged 5 commits intopython:mainfrom Dec 12, 2025
Merged
gh-142374: Fix recursive function cumulative over-counting in sampling profiler#142378pablogsal merged 5 commits intopython:mainfrom
pablogsal merged 5 commits intopython:mainfrom
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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.
pablogsal
commented
Dec 8, 2025
Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
Resolved conflicts by keeping both: - Recursive function deduplication (from pythongh-142374 branch) - Opcode tracking with extract_lineno/normalize_location (from upstream)
fatelei
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to fatelei/cpython
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Dec 12, 2025
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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.