[chrony-users] Massive difference between NTP clocks and PHC

[Denys Rtveliashvili <denys@xxxxxxxxxxxxxxxxxx>]

Hello,

I have tried adding PHC to the configuration of chrony and see things 
like this:

MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
#x PHC0                          0   3   377    11 -322ms[ -322ms] 
+/-    2ns
^* ntp-clock-1                   1   4   377    11 -2579ns[-4000ns] +/-  
441us
^- ntp-clock-2                   1   4   377    11 -2000ns[-2000ns] 
+/-   31ms


322ms is a huge offset and I wonder if anybody has an idea of what could 
be the root source.

ntp-clock-1 and ntp-clock-2 are two proper grandmasters.
ntp-clock-2 is geographically far.
ntp-clock-1 is in the same location.

PHC0 is a clock on an Intel card running under igb driver.
The PTP port of the card is connected to a PTP-enabled Cisco Nexus 
switch, which is connected to a PTP grandmaster. The same grandmaster in 
fact, which is also a NTP source ntp-clock-1.

I would understand 36 secons of a difference (TIA vs GMT) or some 
microseconds of a difference (some network and PCIE jitter). But a third 
of a second is very strange.
Do you have any ideas?

By the way, for synchronization of on-the-NIC PTP clock I tried using 
ptp4l in both software and hardware mode and that did not make any 
difference.

With kind regards,
Denys Rtveliashvili

--
To unsubscribe email chrony-users-request@xxxxxxxxxxxxxxxxxxxx 
with "unsubscribe" in the subject.
For help email chrony-users-request@xxxxxxxxxxxxxxxxxxxx 
with "help" in the subject.
Trouble?  Email listmaster@xxxxxxxxxxxxxxxxxxxx.