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[SR-8519] Linux standardizingPath syscall performance #51039

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keith opened this issue Aug 11, 2018 · 2 comments
Closed

[SR-8519] Linux standardizingPath syscall performance #51039

keith opened this issue Aug 11, 2018 · 2 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior.

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@keith
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keith commented Aug 11, 2018

Previous ID SR-8519
Radar None
Original Reporter @keith
Type Bug
Status Resolved
Resolution Done

Attachment: Download

Additional Detail from JIRA
Votes 1
Component/s
Labels Bug
Assignee None
Priority Medium

md5: 2c4295836ad4a7d07ca26d25e1a3c884

Issue Description:

Currently if you call NSString's `standardizingPath`, you end up calling FileManager's `attributesOfItem` API. This call calls some system API, specifically `getpwuid` and `getgrgid`. These can take a huge amount of time to complete, and the result of them isn't needed in this case, since the only thing we need to know is if the path is a symlink.

In this case it would much faster to directly call lstat, or a different version of `attributesOfItem` that didn't fetch these unused attributes.

In our case, removing this from an IO heavy CLI took run time for some operations from 18 minutes to 4 seconds.

Attached is a flame graph captured using perf with an example (it can be viewed in Safari).
@spevans
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spevans commented Aug 15, 2018

apple/swift-corelibs-foundation#1662 should hopefully improve things.

@spevans
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spevans commented Aug 25, 2018

This has been merged into master now.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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