linux-kernel - Re: Kernel unable to adjust timeofday

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Message-ID: <47571.1222440706@turing-police.cc.vt.edu>
Date:	Fri, 26 Sep 2008 10:51:46 -0400
From:	Valdis.Kletnieks@...edu
To:	Rafal <newsgroup@...core.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Kernel unable to adjust timeofday

On Fri, 26 Sep 2008 15:29:53 +0200, Rafal said:
> Hello, my system (64bit Ubuntu amd64 box) drifts about 10 seconds per hour
> (i.e. time visible in the system).

First thing to do is figure out why your box has *such* a dreadfully poor
clock. You're drifting at around 3,000 parts-per-million.  NTP is only able
to deal with drifts up to 500 ppm, and most systems clocks are *much* more
stable than that (for instance, my laptop is drifting at 2 ppm at the moment).
The fact you're way outside the sane range leads to trouble...

> When I use adjtime(), or when I use ntpd that uses adjtime() then the
> adjustment is slower then the speed of drift.

... which is why you see this happen.

> The default rate of adjustment seems to be really low, can we set the
> default adjustment rate to be a higher?

The default rate is set fine.  It's simply unable to deal with insane hardware
and/or software.  What kernel are you running on it?

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