Date: Fri, 12 Jan 2001 13:48:58 -0600 From: Dan Nelson <dnelson@emsphone.com> To: tomb <tomb@cgf.net> Cc: hackers@FreeBSD.ORG Subject: Re: Kernel time drifting -0.3% to -50% from H/W clock. Message-ID: <20010112134858.A15232@dan.emsphone.com> In-Reply-To: <3A5EC113.B903E2AF@cgf.net>; from "tomb" on Fri Jan 12 00:32:19 GMT 2001 References: <3A5EC113.B903E2AF@cgf.net>
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In the last episode (Jan 12), tomb said: > The next day I noticed the time was wrong again, and decided to run > ntp to track the time on our master. It tried very hard to keep time > but finally gave up and syslogged me that a manual time change would > be necessary. > > This moring I find that the drift is -50% . > > I don't know much about how kernel time relates to bios time but I > guess that there's a pashe locked loop in the software that is not > getting feedback from the HW clock, but I'm just guessing. > > Can anybody explain what is happening? Try adding the following kernel options and rebuilding: options CLK_USE_I8254_CALIBRATION options CLK_USE_TSC_CALIBRATION That should help some, if the clock the kernel decided to pick really drifts that badly. You can see which clock the kernel is using with "sysctl kern.timecounter.hardware", and view the current timing values for each clock with "sysctl machdep | grep freq". -- Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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