[Twisted-Python] a question about monotonic clock

Phil Mayers p.mayers at imperial.ac.uk
Sun Oct 28 18:05:57 EDT 2012

This depends on how you're running ntpd. If you have "-x" on the command line, yes - ntpd will not step.

If not, there are circumstances it will step - clock diffs in excess of 128ms iirc?

Who knows what newer implementations like chrony or openntpd do!

Glyph <glyph at twistedmatrix.com> wrote:

>On Oct 28, 2012, at 9:01 AM, Christopher Armstrong
><radix at twistedmatrix.com> wrote:
>> I'm not speaking from experience, admittedly. How big exactly are the
>steps in NTP skewing?
>There are two things NTP can do: stepping and slewing.  (Skewing is not
>one of them.)
>If you're stepping, the steps can be arbitrarily large.  This is what
>ntpdate does.
>If you're slewing, there are no steps.  This is what ntpd does.  The
>frequency of your clock is just adjusted up or down by a small
>(configurable) amount.  Generally not enough to affect the pitch or
>network latency of 20ms sound sampling.  In fact, it would generally
>help, not hurt, because the only reason ntp would be issuing a slew is
>that your clock is faster or slower than real time anyway.
>PEP 418 <http://www.python.org/dev/peps/pep-0418/> covers this stuff in
>a lot of detail; especially the glossary.
>Twisted-Python mailing list
>Twisted-Python at twistedmatrix.com

Sent from my mobile device, please excuse brevity and typos.
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