[ntp:questions] Re: ntpd PLL and clock overshoot

Richard B. Gilbert rgilbert88 at comcast.net
Mon Oct 9 18:25:58 UTC 2006


user at domain.invalid wrote:

> Richard,
> 
> The overshoot is the result of a misdirected Solaris/Linux design of the 
> adjtime() system call. The design added a poll to the transfer function 
> in order to speed the response to a programmed offset. The result 
> completely torpedoes the PLL transient response and there is nothing 
> that can be done to correct it in ntpd itself. What you see is what you 
> get. The problem is most apparent with large initial frequency offsets, 
> which are guaranteed to result in pinball behavior. Note the overshoots 
> do not occur in FreeBSD or Tru64, which have a reasonable design.
> 
> Dave

Dave,

Have you reported this to Sun as a bug?

It seems to me that they should fix it and, perhaps, create a new 
function, say, adjtime_fast() that would add the functionality without 
breaking ntpd.  It might not get you anywhere but he who does not ask 
does not get!




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