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[SR-12124] [NumberDate] CFGetSystemUptime for BSD and Windows #3273

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benrimmington opened this issue Feb 4, 2020 · 5 comments
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[SR-12124] [NumberDate] CFGetSystemUptime for BSD and Windows #3273

benrimmington opened this issue Feb 4, 2020 · 5 comments
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Foundation Improvement

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@benrimmington
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Previous ID SR-12124
Radar rdar://problem/59216628
Original Reporter @benrimmington
Type Improvement
Additional Detail from JIRA
Votes 0
Component/s Foundation
Labels Improvement
Assignee None
Priority Medium

md5: 69fb038c8490173be7492fcf9739e539

Issue Description:

Re: CFGetSystemUptime — use CLOCK_UPTIME for BSD, and QueryUnbiasedInterruptTimePrecise for Windows?

CLOCK_MONOTONIC is the correct choice for Linux and Cygwin, because it excludes system "downtime" on those platforms.

CLOCK_UPTIME is available on FreeBSD and OpenBSD, so it might be a better option for TARGET_OS_BSD.

GetTickCount64 may include system "downtime", and the result is in milliseconds, which might not be precise enough. For example, ProcessInfo.processInfo.systemUptime is currently used by swift-corelibs-xctest.

QueryUnbiasedInterruptTimePrecise excludes system "downtime", and the result is in 100-nanosecond units. It is also used by Cygwin and Dispatch for the same purpose.
@benrimmington
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Cc: @compnerd

@beccadax
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beccadax commented Feb 6, 2020

@swift-ci create

@benrimmington
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Cc: 3405691582 (JIRA User)

@swift-ci
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Comment by 3405691582 (JIRA)

👍

@swift-ci
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swift-ci commented Mar 8, 2021

Comment by 3405691582 (JIRA)

Just something to think about since I brushed up against this recently: on OpenBSD at least, CLOCK_MONOTONIC and CLOCK_UPTIME are reasonably close, but a lot of Foundation uses MONOTONIC which Dispatch may interpret as UPTIME since it is trying to do stuff like clock inference (c.f. https://github.com/apple/swift-corelibs-libdispatch/blob/f13ea5dcc055e5d2d7c02e90d8c9907ca9dc72e1/src/shims/time.h#L257). I don't have any solutions or ideas for this right now, but it's something interesting to think about.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 5, 2022
@benrimmington benrimmington closed this as not planned Won't fix, can't repro, duplicate, stale Jan 12, 2023
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