RE: [EXTERNAL] Re: [chrony-users] time sync query

["Jahagirdar, Bhushan" <Bhushan.Jahagirdar@xxxxxxxxxx>]

Hi Miroslav,

Attaching the log files.
Please let me know if you need more data to analyze the use case.

I will again describe the use case that I am testing on my embedded system:
Version of chrony: 2.2.1
Time source : GPS time. Fed through refclock as GPS is connected on other controller than SOC.
Use cases:
1. At system boot up, epoch time should be set to GPS time. --> works well
2. At run time feed bigger time offset for some time and then again start feeding correct GPS data. In this use case I see, chrony is able to set GPS data in case if the offset is smaller or any offset fed for very short time.. But if it's bigger offset is fed, then it never syncs the time back soon; at least not within a minute. I need to know the relation between offset, amount of time chrony might need to sync the offset and source stability.

BR,
Bhushan.

-----Original Message-----
From: Miroslav Lichvar [mailto:mlichvar@xxxxxxxxxx] 
Sent: Tuesday, August 08, 2017 5:53 PM
To: chrony-users@xxxxxxxxxxxxxxxxxxxx
Subject: Re: [EXTERNAL] Re: [chrony-users] time sync query

On Tue, Aug 08, 2017 at 12:07:11PM +0000, Jahagirdar, Bhushan wrote:
> Offset of the reference is not jumping as I am constantly feeding data every one sec.
> May I know what is the max offset range that chrony can consider to correct it.

If you have enabled makestep, it doesn't matter how large is the offset. But it does matter how stable it is. The default value of maxdistance is 3 seconds, which includes the jitter of the refclock.
In your case the reported distance (the +/- value) was in hours.

> I have already experimented about makestep and found that even if the time is set to epoch, for initial feeds the time gets corrected. But what if abruptly I am setting the time to epoch then I see chrony is not able to sync. 
> I am trying to test the working of chrony on typical embedded system.

Can you please post the refclocks and statistics logs? We should better see what is happening.

--
Miroslav Lichvar

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