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`<filesystem>`: Improve `symlink_status` performance by nikola-sh · Pull Request #5071 · microsoft/STL · GitHub
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<filesystem>: Improve symlink_status performance #5071

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Merged
merged 9 commits into from
Nov 14, 2024
Merged

<filesystem>: Improve symlink_status performance #5071

merged 9 commits into from
Nov 14, 2024

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@nikola-sh
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@nikola-sh nikola-sh commented Nov 9, 2024 •
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_Get_any_status(__Path, __std_fs_stats_flags::_Attributes | __std_fs_stats_flags::_Reparse_tag) calls to many WinAPI functions for regular files or directories. It calls GetFileAttributesEx + CreateFile + GetFileInformationByHandleEx(FileBasicInfo) but GetFileAttributesEx is enough to get all needed data if it is known that a file is not a reparse point.
This problem affects symlink_status performance.

Benchmark symlink_status results before changes:

---------------------------------------------------------
Benchmark               Time             CPU   Iterations
---------------------------------------------------------
symlink_status      15376 ns        15346 ns        44800

Benchmark symlink_status results after changes:

---------------------------------------------------------
Benchmark               Time             CPU   Iterations
---------------------------------------------------------
symlink_status       2219 ns         2148 ns       320000

@nikola-sh nikola-sh marked this pull request as ready for review November 9, 2024 19:52
@nikola-sh nikola-sh requested a review from a team as a code owner November 9, 2024 19:52
@CaseyCarter CaseyCarter added the performance Must go faster label Nov 9, 2024
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AlexGuteniev
AlexGuteniev reviewed Nov 10, 2024
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@StephanTLavavej StephanTLavavej self-assigned this Nov 10, 2024
@StephanTLavavej StephanTLavavej added the filesystem C++17 filesystem label Nov 10, 2024
StephanTLavavej
StephanTLavavej reviewed Nov 11, 2024
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Thanks! On my system (5950X, 24H2, Samsung SSD 980 PRO), I observe much less of a performance improvement, but still major: 21126 ns => 10098 ns, for a speedup of 2.1x.

@StephanTLavavej StephanTLavavej mentioned this pull request Nov 10, 2024
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Thanks! On my system (5950X, 24H2, Samsung SSD 980 PRO), I observe much less of a performance improvement, but still major: 21126 ns => 10098 ns, for a speedup of 2.1x.

Thank you too!
Yes, performance improvement depends on filesystem minifilter drivers configuration.
For example, for paths on system drive GetFileAttributes works much slower than for paths from other drives.

@StephanTLavavej StephanTLavavej changed the title Improve symlink_status performance <filesystem>: Improve symlink_status performance Nov 12, 2024
@StephanTLavavej StephanTLavavej self-assigned this Nov 14, 2024
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

@CaseyCarter CaseyCarter removed their assignment Nov 14, 2024
@StephanTLavavej StephanTLavavej merged commit c18bcea into microsoft:main Nov 14, 2024
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Thanks again, and congratulations on your first microsoft/STL commit! 😻 🎉 💾

This change is expected to ship in VS 2022 17.13 Preview 3.

@nikola-sh nikola-sh deleted the fix_symlink_status branch November 14, 2024 22:37
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@StephanTLavavej StephanTLavavej StephanTLavavej approved these changes

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@CaseyCarter CaseyCarter CaseyCarter approved these changes

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filesystem C++17 filesystem performance Must go faster

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