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Date:      Fri, 23 Aug 2002 23:37:57 +0200
From:      Poul-Henning Kamp <phk@critter.freebsd.dk>
To:        John Polstra <jdp@polstra.com>
Cc:        current@freebsd.org
Subject:   Re: how to compute the skew between TSC in SMP systems ? 
Message-ID:  <30560.1030138677@critter.freebsd.dk>
In-Reply-To: Your message of "Fri, 23 Aug 2002 14:35:35 PDT." <200208232135.g7NLZZqx088123@vashon.polstra.com> 

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In message <200208232135.g7NLZZqx088123@vashon.polstra.com>, John Polstra write
s:

Still, the feature has come in handy when debugging certain
>multiprocessor situations where I really needed to know the relative
>ordering of events taking place on both CPUs.

Right, you might get away with that in tightly controlled circumstances,
but it would probably be far smarter to use the counter in the
IOAPIC (exists on all SMP) or the ACPI counter even in such cases.

-- 
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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