| Re: [chrony-dev] [GIT] chrony/chrony.git branch, master, updated. 1.26-26-g9a01ccc |
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On Tue, Nov 15, 2011 at 06:55:18PM +0100, git@xxxxxxxxxxxxx wrote:
> Add corrtimeratio directive
>
> The corrtimeratio directive controls the ratio between the
> duration in which the clock is slewed for an average correction
> according to the source history and the interval in which the
> corrections are done (usually the NTP polling interval). Corrections
> larger than the average take less time and smaller corrections take
> more time, the amount of the correction and the correction time are
> inversely proportional.
>
> Increasing corrtimeratio makes the overall frequency error of
> the system clock smaller, but increases the overall time error as
> the corrections will take longer.
>
> By default, the ratio is 1, which means the duration of an average
> correction will be close to the update interval.
I'm not sure about the terminology and I'm open for suggestions for a
better name for this option.
In my testing the RMS frequency error can improve by factor 10 or even
more and with larger corrtimeratio it can be even better than with ntpd.
It seems there is always a compromise between time and frequency
error. The default is set so the time error is not noticeably worse
than it was before.
The graphs of the clock offset now look much nicer too:
http://mlichvar.fedorapeople.org/tmp/chrony_corr.png
--
Miroslav Lichvar
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