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To: Nate Lawson <nate@root.org>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Sun, 06 Apr 2003 13:39:27 PDT."
             <Pine.BSF.4.21.0304061338460.23366-100000@root.org> 
Date: Sun, 06 Apr 2003 23:22:17 +0200
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cc: des@ofug.org
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cc: Tor.Egge@cvsup.no.freebsd.org
Subject: Re: cvs commit: src/sys/conf options.i386 src/sys/i386/i386 tsc.c
	src/sys/i386/conf NOTES 
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In message <Pine.BSF.4.21.0304061338460.23366-100000@root.org>, Nate Lawson wri
tes:
>On Sun, 6 Apr 2003 Tor.Egge@cvsup.no.freebsd.org wrote:
>> > Is there a simple procedure to determine whether the TSCs on any given
>> > multi-CPU machine are synchronized?
>> 
>> Ensure that the TSCs are used, then run a program which calls
>> gettimeofday() in a loop and prints an error message each time the
>> clock steps backwards.  Repeat procedure after 1 day of uptime.
>
>Perhaps you could enable this option by default if it had a corresponding
>check for drift that would disable it if things got out of hand.

It will require considerable statistics to convince me to enable
TSC on SMP systems in general or by default.

-- 
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.