| Re: [chrony-users] Massive difference between NTP clocks and PHC |
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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 |____ unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1 ____|____ and Gravity ______|_ www.theory.physics.ubc.ca/
On Fri, 14 Oct 2016, Denys Rtveliashvili wrote:
Hello,
I have tried adding PHC to the configuration of chrony and see things like
What is PHC? Could it be trailing-vs-leading-edge-of-a-pulse problem?
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
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