NTPD unable to adjust local clock
joerg at britannica.bec.de
Wed Apr 6 11:39:31 PDT 2005
On Tue, Apr 05, 2005 at 06:44:33PM -0700, Matthew Dillon wrote:
> I've investigated this a bit more. OpenBSD's ntpd is just not up to
> snuff. It has no PLL locking code at all and the result is that the
> timekeeping is constantly out of whack, oscillating back and forth as
> ntpd does its occassional adjtime() based corrections. If it isn't
> out of whack due to the clock being fast or slow, it's out of whack due
> to the adjtime() call trying to correct 5 minutes worth of creep with a
> single call. My test boxes are oscillating between -10ms and +25ms of
> error and they have fairly accurate clocks. Any boxes with inaccurate
> clocks are going to be hit hard. A 1 second error is easy to accumulate
> with a clock that is only 0.3% off.
Well, I get differences between ntp0.fau.de and ntps1-1.cs.tu-berlin.de
of 0.003, so the system time oscillating somewhat is not critial.
After watching the output of ntpd for a while, there seems to be a bug.
The offset goes down from initially 1.138025 to 0.048019 and 0.024507,
but it gets addjusted to 0.663717s right afterwards. That's bogus.
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