Re: Bug report: `maxslewrate` violation by chrony

Thank you, this indeed appears to be our issue.

On Tue, Dec 6, 2022, 00:47 Miroslav Lichvar <[email protected]> wrote:

> On Mon, Dec 05, 2022 at 05:14:10PM -0800, Adam Snaider wrote:
> > Hi folks,
> >
> > I wanted to report a bug. We use chrony for time synchronization and we
> > have a strict requirement that forces us to limit the slew rate to no
> more
> > than 250ppm. We noticed that in some conditions, chrony exceeds this
> limit
> > by >10x. I've collected an strace that shows chrony is indeed the culprit
> > as it is calling the clock_adjtime syscall with the tick and frequency
> set
> > to 9980 and -140765 which corresponds to roughly -2002ppm.
>
> The values passed to clock_adjtime() correct both the estimated
> frequency error (drift) and phase error (slew). What frequency do you
> see reported in the tracking log when this happens?
>
> If I understand your test correctly, you are simulating an unstable
> clock, which could be measured as a large frequency offset.
>
> If you need to limit the sum of the two, you will need to set also
> the maxdrift option.
>
> --
> Miroslav Lichvar
>
>
> --
> To unsubscribe email chrony-users-request-kWFZVVI9zxvPqho9SqqRMmD2FQJk+8+b@public.gmane.org
> with "unsubscribe" in the subject.
> For help email chrony-users-request-kWFZVVI9zxvPqho9SqqRMmD2FQJk+8+b@public.gmane.org
> with "help" in the subject.
> Trouble?  Email [email protected]
>
>