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Date:      Tue, 13 Sep 2011 08:17:42 -0400
From:      John Baldwin <jhb@freebsd.org>
To:        freebsd-hackers@freebsd.org
Cc:        Brett Glass <brett@lariat.net>
Subject:   Re: Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system
Message-ID:  <201109130817.42232.jhb@freebsd.org>
In-Reply-To: <201109122153.PAA20860@lariat.net>
References:  <201109111852.MAA08146@lariat.net> <14112_1315854090_4E6E570A_14112_184_1_D9B37353831173459FDAA836D3B43499C803FA06@WADPMBXV0.waddell.com> <201109122153.PAA20860@lariat.net>

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On Monday, September 12, 2011 5:53:39 pm Brett Glass wrote:
> More information regarding the odd behavior I'm seeing. Turns out
> that packets do not even need to leave the machine for it to
> report large negative ping times, on the order of more than half
> a second. (See below.) Clearly something is odd about timekeeping
> in this system (SiS motherboard chipset, PII-generation Celeron
> but still effectively a "686") which was not a problem when it was
> running FreeBSD 4.11-RELEASE (as it was before). Any ideas?

4.x didn't support the ACPI timer.

I would look at the kern.timecounter sysctls.  Maybe try forcing it to use the 
TSC.

-- 
John Baldwin



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