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To: John Baldwin <jhb@freebsd.org>
Subject: Re: Change default VFS timestamp precision?
In-reply-to: <201412181436.31701.jhb@freebsd.org>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
References: <201412161348.41219.jhb@freebsd.org>
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Date: Thu, 18 Dec 2014 20:05:00 +0000
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Cc: "freebsd-arch@freebsd.org" <arch@freebsd.org>,
 Adrian Chadd <adrian@freebsd.org>, Jilles Tjoelker <jilles@stack.nl>
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--------
In message <201412181436.31701.jhb@freebsd.org>, John Baldwin writes:

>> >Surely there has to be better ways of doing this stuff. Computers keep
>> >getting faster; it wouldn't be out of the realm of possibility that we
>> >could see a compiler read, compile and spit out a .o inside of a
>> >millisecond. (Obviously not C++, but..)
>> 
>> A millisecond is pushing it, all things considered, it would have to
>> be an utterly trivial source file for a utterly trivial language.

>Eh, the use case I most care about is back-to-back updates to a directory on
>an NFS server.

My comments above was only about compilers in reference to Adrians point.

>I don't understand
>why you think TSP_USEC is slower than TSP_NSEC.  microtime() and nanotime()
>both just call bintime() and then convert the result using similar math.

Because of the pointless nano->micro conversion which makes TSP_USEC
take a division longer to deliver a less precise result than TSP_NSEC.

-- 
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.