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 id 1eVeQG-000GIo-RE; Sun, 31 Dec 2017 14:17:08 +0000
Date: Sun, 31 Dec 2017 14:17:08 +0000
From: Gary Palmer <gpalmer@freebsd.org>
To: freebsd-stable@freebsd.org
Subject: Odd behaviour on recent boot of 11.1 with timecounters
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Hi,

I recently updated to 11.1-RELEASE-p6 and on the most recent reboot 
(after rebuilding all the necessary packages) the clock was running 
slow and NTP wouldn't sync.  I looked in /var/log/messages and I found
that for some reason, on this latest boot, it got the frequency of
TSC-low wrong.

Aug 24 04:55:35 my kernel: Timecounter "TSC-low" frequency 1746073190 Hz quality 1000
Aug 26 03:11:38 my kernel: Timecounter "TSC-low" frequency 1746070760 Hz quality 1000
Aug 26 14:12:46 my kernel: Timecounter "TSC-low" frequency 1746075204 Hz quality 1000
Nov 19 16:01:09 my kernel: Timecounter "TSC-low" frequency 1746070746 Hz quality 1000
Dec 27 22:28:00 my kernel: Timecounter "TSC-low" frequency 1746074808 Hz quality 1000
Dec 27 22:51:12 my kernel: Timecounter "TSC-low" frequency 1746071892 Hz quality 1000
Dec 28 12:50:46 my kernel: Timecounter "TSC-low" frequency 1746069704 Hz quality 1000
Dec 28 14:03:52 my kernel: Timecounter "TSC-low" frequency 1937876448 Hz quality 1000

Until the December reboots the machine was running 10.x.  Dec 27 and later
are part of the process to get up to 11.x.

Any idea why the TSC-low frequency jumped 191,806,744Hz on the last
measurement?

I switched to HPET temporarily via sysctl and ntp seems happy.  I'm just
concerned that the problem might recur on later reboots as TSC-low seems
to be the preferred timecounter.

Thanks,

Gary