Re: [chrony-users] Chrony not taking SOCKET data from Application

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On Thu, Feb 02, 2023 at 11:52:12AM +0530, sarveshwar k wrote:
> Hi Miroslav,
> I have enabled the refclocks logs where I see the PPS signal are available.
> And GPS UTC time comes very fast within a second.
> Attaches is the refclocks logs. Can you please review once?

Please don't post such large files to the list. Few hundred lines of
each would be enough, or if needed, upload it on a file hosting
service and just post the links here.

The logs mostly look good to me. There are some larger offset, but
it's difficult to tell what is the cause. Could be varying load on the
CPU, unstable temperature, etc.

The reason for chronyc sources sometimes showing 2 as LastRx, even
when no samples are lost, seems to be incorrect rounding of the sample
time. I can fix that.

> CPU is running good and power saving features are not there. Not tried with
> higher PPS rate. Using pps-gpio-poll as kernel module, I see the CPU gets
> occupied waiting for the edge of clock right.

Right, it's polling for the pin to change. It's more accurate, but
comes at a cost of the CPU load.

> Through which parameter of chronyc output can we know the synchronization
> is in micro/nano/seconds?

The RMS offset in tracking report is an indicator of stability. To
determine accuracy you would need a more accurate time source, e.g. a
NIC with HW-timestamping PPS input.

> I have made makestep to step if difference is more than 100ns continuously,
> with which I see the system time  is many times 0 seconds slower than NTP
> time (from the output of tracking). Does this configuration effects
> anything.

That doesn't do anything useful. It's just stepping the clock to the
current estimate of true time.

Miroslav Lichvar

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