From owner-freebsd-arch  Fri Oct 26 15: 1:43 2001
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To: Matthew Dillon <dillon@apollo.backplane.com>
Cc: John Baldwin <jhb@FreeBSD.ORG>, arch@FreeBSD.ORG,
	Peter Wemm <peter@wemm.org>, Bakul Shah <bakul@bitblocks.com>
Subject: Re: 64 bit times revisited.. 
In-Reply-To: Your message of "Fri, 26 Oct 2001 14:50:22 PDT."
             <200110262150.f9QLoMB38937@apollo.backplane.com> 
Date: Sat, 27 Oct 2001 00:01:06 +0200
Message-ID: <9133.1004133666@critter.freebsd.dk>
From: Poul-Henning Kamp <phk@critter.freebsd.dk>
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In message <200110262150.f9QLoMB38937@apollo.backplane.com>, Matthew Dillon wri
tes:
>
>:    The best kernel-internal time representnation is ticks, with a simple
>:    baseline cache mechanism to convert it to other formats (e.g. as
>:    required by NFS, UFS, userland, etc...).  Nothing beats ticks...
>:    a binary fixed point format doesn't even come *close* to being better
>:    then straight ticks.
>:
>
>    Before this gets misinterpreted, the 'ticks' I am talking about is 
>    not the kernel timer interrupt ticks... it's the high resolution cpu
>    or 825x ticks we get.  e.g. frequency dependant on the timer we use.

Matt, that is the mess Linux is fighting with.  We have had a superior
solution for years by now which even allows us to change timekeeping
hardware on the fly as we find more suitable timebases.

-- 
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.

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