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To: Jilles Tjoelker <jilles@stack.nl>
Subject: Re: Change default VFS timestamp precision?
In-reply-to: <20141219194800.GA29107@stack.nl>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
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Date: Fri, 19 Dec 2014 19:49:28 +0000
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Cc: "freebsd-arch@freebsd.org" <arch@freebsd.org>,
 Adrian Chadd <adrian@freebsd.org>
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--------
In message <20141219194800.GA29107@stack.nl>, Jilles Tjoelker writes:
>On Fri, Dec 19, 2014 at 05:41:01PM +0000, Poul-Henning Kamp wrote:
>> In message <7567696.mqJ3jgzJgL@ralph.baldwin.cx>, John Baldwin writes:
>
>> >Yes, and multiplication is cheaper than division.  It's not a power of
>> >two (so more than a single bitshift), but possibly in the noise compared
>> >to the work in bintime() itself.
>
>> But why not use nanosecond resolution given that the cost is cheaper ?
>
>Because there is no API to set timestamps with nanosecond resolution,
>and therefore a cp -p copy of a file will appear older than the original
>with 99.9% probability. I think that is undesirable.

Hmm, good point, I forgot about that screwup...

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.