[ntp:questions] Startup transient with missing drift file
Richard B. gilbert
rgilbert88 at comcast.net
Sun Apr 8 13:29:48 UTC 2007
Hal Murray wrote:
> What should it look like? How long should it take to get stable?
> I was expecting ntpd to think for a while, then jump to close to
> the right value, then converge to the final value. I'd expect
> that to take an hour or so.
> What I'm seeing (recent ntp-dev) is that the jump doesn't get
> very close and the converge part takes multiple hours, depending
> upon how far off the jump was.
> Has anybody else watched a startup transient recently?
> I've been looking at a lot of them while chasing a Linux
> glitch that doesn't compute the CPU frequency repeatably.
> What should happen if I start with an explicit drift value
> that is way off?
I'd expect to see ntpd take a good deal more time pulling in to tight
synchronization. Startup is pretty raggedy anyway thanks to a
non-linearity introduced into (I think, adjtimex()) to make it correct
errors more quickly. The nonlinearity messed up Dave's calculations so
you get an overshoot
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