Description

mdboom

opened on Jul 2, 2024

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Bug description:

#118450 "Convert the evaluation stack to stack refs" (by @Fidget-Spinner) unfortunately seems to have introduced a 7% - 11% performance regression overall (though as much as 25% for some benchmarks) on Windows only. Linux (both x86_64 and aarch64) and macOS (arm) seem to have a change beneath the noise threshold. To be clear, @Fidget-Spinner's work is great and the lesson here is that for these sorts of sweeping low-level changes, we should have benchmarked on all of the Tier 1 platforms to be certain.

I don't know what the cause is -- it is probably MSVC not being able to "optimize through" something and introducing unnecessary overhead, but that's just a theory.

Cc: @brandtbucher, @markshannon

CPython versions tested on:

CPython main branch

Operating systems tested on:

Windows

Linked PRs

• gh-121263: Macro-ify most stackref functions for MSVC #121270

Activity

1. mdboom

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   performancePerformance or resource usagePerformance or resource usage

   OS-windows

   on Jul 2, 2024
2. Fidget-Spinner commented on Jul 2, 2024

   

   Fidget-Spinner

   on Jul 2, 2024

   Member

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   @mdboom Thanks for bringing this up! In the past this was usually due to MSVC not being able to inline in the eval loop because its too big of a function. I can change all the static inlines to macros and try benchmarking again?
3. mdboom commented on Jul 2, 2024

   

   mdboom

   on Jul 2, 2024

   ContributorAuthor

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   I can change all the static inlines to macros and try benchmarking again?

   Sounds like a good first thing to try. Thanks!
4. Eclips4

   added

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   3.14bugs and security fixesbugs and security fixes

   on Jul 2, 2024
5. Fidget-Spinner

   added a commit that references this issue on Jul 3, 2024

   gh-121263: Macro-ify most stackref functions for MSVC (GH-121270)

   722229e
6. mdboom

   closed this as completedon Jul 3, 2024
7. estyxx

   added a commit that references this issue on Jul 17, 2024

   pythongh-121263: Macro-ify most stackref functions for MSVC (pythonGH…

   d2927af
8. mdboom

   added a commit that references this issue on Jul 19, 2024

   Revert "pythongh-121263: Macro-ify most stackref functions for MSVC (p…

   0853d0e

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