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Re: [gpsd-dev] Mysteriously vanishing bugs don't make me happy


From: Miroslav Lichvar
Subject: Re: [gpsd-dev] Mysteriously vanishing bugs don't make me happy
Date: Tue, 5 Nov 2013 11:27:00 +0100
User-agent: Mutt/1.5.21 (2010-09-15)

On Mon, Nov 04, 2013 at 02:55:19PM -0800, Gary E. Miller wrote:
> "Eric S. Raymond" <address@hidden> wrote:
> > Gary E. Miller <address@hidden>:
> > > FYI, after many days of running chronyd my clock stability is now
> > > down to +/- 400 nSec.  Yes, nSec, not uSec, but it takes a while to
> > > get there.

Is that the RMS offset value from chronyc tracking? That is a long
term statistic and it may take a long time to reach the minimum if
there was a large offset corrected on start. With poll 4, chronyd
should be able to settle down in minutes, not days.

> > What seems off about this is that (I think) you've mentioned chronyd
> > taking nanosecond-scale corrections before, yet the TSOTV steps
> > precision down to microseconds. Is this correct?
> 
> Yes, it is correct.  The correction is in nSec, the time to be corrected
> is in uSec.  It makes no sense, but that is their documented interface and
> it works quite well.

The important information is the offset, which is sent as floating
point number. The information when was the offset measured doesn't
need that much resolution, milliseconds would probably be still more
than enough for all practical purposes.

-- 
Miroslav Lichvar



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