Re: Chrony not taking SOCKET data from Application

Why would you be using makestep if the difference were more than 100ns. That
both seems extreme and totally subverts the action of chrony. Chrony is
designed to correct the system clock to the best estimate of the true time and
rate. Makestep ruins that, especially the rate estimate. Nothing can control
the clock to 100ns unless you have very special hardware. 100ns is less than
100 ft of cable, and needs very special impedance matching to attain.


William G. Unruh __| Canadian Institute for|____ Tel: +1(604)822-3273
Physics&Astronomy _|___ Advanced Research _|____ Fax: +1(604)822-5324
UBC, Vancouver,BC _|_ Program in Cosmology |____ [email protected]
Canada V6T 1Z1 ____|____ and Gravity ______|_    theory.physics.ubc.ca/

On Wed, 28 Jun 2023, sarveshwar k wrote:

> [CAUTION: Non-UBC Email]Hi Miroslav,
> > Verify that the process which syncs the system clock on start from the
> > external RTC doesn't do that again later. Other than that I have no
> > idea what could be wrong.
> System time is updated with RTC once and when 3D fix is received, system time is corrected to GPS time
> using Chronyd (as I am sending the GPS time using Unix Domain Socket to chrony. Chronyd uses PPS as a
> trusted source).
> The chronyc sources output shows large offset in milliseconds during the first 3 samples.
> 
> One clarification on another item related to Chronyd:
> - I am using the makestep directive (which does continuously if the difference is more than 100ns) in the
> config file. Does chronyd adjusting the system time affects the CLOCK_MONOTONIC as well? 
> 
> Thanks & Regards
> Sarveshwar.K
> 
> On Tue, May 9, 2023 at 12:45 PM Miroslav Lichvar <[email protected]> wrote:
>       On Mon, May 08, 2023 at 12:09:16PM +0530, sarveshwar k wrote:
>       > Hi Miroslav,
>       >
>       > My Implementation is as below:
>       > - We have external RTC, which is used to sync system time on initialization
>       > based on 1PPS from external RTC
>       > - And on receiving GNSS 3D fix, the GPS UTC time is sent to chrony over
>       > Unix Domain Socket.
>       > - And we sync RTC for every 10 seconds on GNSS 1PPS (so that RTC is close
>       > to the UTC time in seconds)
>
>       > Can you please support on debugging what can be the issue.
>
>       Verify that the process which syncs the system clock on start from the
>       external RTC doesn't do that again later. Other than that I have no
>       idea what could be wrong.
>
>       --
>       Miroslav Lichvar
> 
>
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