Re: Question about large gap of offset on phc2sys with chrony

+ [email protected]

On Fri, Aug 5, 2022 at 11:14 AM 심준영 <[email protected]> wrote:

> Hi all,
>
> I have a problem on my system environment using chrony and linuxptp.
>
> There are two machines on my local network. One is ptp4l master and
> another is
> ptp4l slave. The ptp4l master machine uses chrony to update system clock
> and
> also phc2sys updates PTP hardware clock from system clock.
>
> The ptp4l slave machine doesn't use chrony and any NTP daemon, it updates
> system clock using phc2sys from PTP hardware clock.
>
> My problem is to cause too large gap between system clock and PTP hardware
> clock
> for a short while, whenever chrony synchronizes time from external NTP
> server
> (Poll is 6, so about 64 seconds) and then will affect to PTP hardware
> clock and
> system clock of the ptp4l slave machine.
>
> Are there any ideas to keep stable small gap even though using NTP like
> chrony
> to update system clock?
>
> Below is a phc2sys log from ptp4l master machine. The offset increases to
> -2136ns from under 100ns when chrony synchronizes time from external NTP
> server.
>
> ...
> Aug  5 10:54:56 my-machine phc2sys: [9332.901] eth0 sys offset       -39
> s2 freq  -73487 delay   2250
> Aug  5 10:54:57 my-machine phc2sys: [9333.901] eth0 sys offset       -53
> s2 freq  -73512 delay   1875
> Aug  5 10:54:58 my-machine phc2sys: [9334.902] eth0 sys offset       -15
> s2 freq  -73490 delay   2250
> Aug  5 10:54:59 my-machine phc2sys: [9335.902] eth0 sys offset        76
> s2 freq  -73404 delay   1750
> Aug  5 10:55:00 my-machine phc2sys: [9336.902] eth0 sys offset       -11
> s2 freq  -73468 delay   1875
> Aug  5 10:55:01 my-machine phc2sys: [9337.903] eth0 sys offset        29
> s2 freq  -73431 delay   2000
> Aug  5 10:55:02 my-machine phc2sys: [9338.903] eth0 sys offset       -38
> s2 freq  -73489 delay   1875
> Aug  5 10:55:03 my-machine phc2sys: [9339.903] eth0 sys offset         4
> s2 freq  -73459 delay   2000
> Aug  5 10:55:04 my-machine phc2sys: [9340.904] eth0 sys offset        17
> s2 freq  -73445 delay   2000
> Aug  5 10:55:05 my-machine phc2sys: [9341.904] eth0 sys offset       -15
> s2 freq  -73472 delay   2000
> Aug  5 10:55:06 my-machine phc2sys: [9342.904] eth0 sys offset         0
> s2 freq  -73461 delay   2000
> Aug  5 10:55:07 my-machine phc2sys: [9343.905] eth0 sys offset        16
> s2 freq  -73445 delay   1875
> Aug  5 10:55:08 my-machine phc2sys: [9344.905] eth0 sys offset       -23
> s2 freq  -73479 delay   2000
> Aug  5 10:55:09 my-machine phc2sys: [9345.905] eth0 sys offset         2
> s2 freq  -73461 delay   2000
> Aug  5 10:55:10 my-machine phc2sys: [9346.906] eth0 sys offset        33
> s2 freq  -73430 delay   1751
> Aug  5 10:55:11 my-machine phc2sys: [9347.906] eth0 sys offset       -62
> s2 freq  -73515 delay   2125
> Aug  5 10:55:12 my-machine phc2sys: [9348.906] eth0 sys offset         8
> s2 freq  -73463 delay   2000
> Aug  5 10:55:13 my-machine phc2sys: [9349.907] eth0 sys offset     -2136
> s2 freq  -75605 delay   2000
> Aug  5 10:55:14 my-machine phc2sys: [9350.907] eth0 sys offset     -2363
> s2 freq  -76473 delay   1875
> Aug  5 10:55:15 my-machine phc2sys: [9351.907] eth0 sys offset     -1656
> s2 freq  -76475 delay   1875
> Aug  5 10:55:16 my-machine phc2sys: [9352.908] eth0 sys offset      -919
> s2 freq  -76234 delay   2000
> Aug  5 10:55:17 my-machine phc2sys: [9353.908] eth0 sys offset      -571
> s2 freq  -76162 delay   1875
> Aug  5 10:55:18 my-machine phc2sys: [9354.908] eth0 sys offset      -176
> s2 freq  -75938 delay   1875
> Aug  5 10:55:19 my-machine phc2sys: [9355.909] eth0 sys offset         8
> s2 freq  -75807 delay   2000
> Aug  5 10:55:20 my-machine phc2sys: [9356.909] eth0 sys offset       -71
> s2 freq  -75884 delay   2000
> Aug  5 10:55:21 my-machine phc2sys: [9357.909] eth0 sys offset       119
> s2 freq  -75715 delay   1750
> Aug  5 10:55:22 my-machine phc2sys: [9358.910] eth0 sys offset       -49
> s2 freq  -75847 delay   2000
> Aug  5 10:55:23 my-machine phc2sys: [9359.910] eth0 sys offset        53
> s2 freq  -75760 delay   2250
> Aug  5 10:55:24 my-machine phc2sys: [9360.911] eth0 sys offset       -22
> s2 freq  -75819 delay   2000
> Aug  5 10:55:25 my-machine phc2sys: [9361.911] eth0 sys offset        25
> s2 freq  -75779 delay   2000
> Aug  5 10:55:26 my-machine phc2sys: [9362.912] eth0 sys offset        46
> s2 freq  -75750 delay   2000
> Aug  5 10:55:27 my-machine phc2sys: [9363.912] eth0 sys offset       -17
> s2 freq  -75799 delay   2000
> Aug  5 10:55:28 my-machine phc2sys: [9364.912] eth0 sys offset       -44
> s2 freq  -75832 delay   2000
> Aug  5 10:55:29 my-machine phc2sys: [9365.913] eth0 sys offset       -38
> s2 freq  -75839 delay   2000
> Aug  5 10:55:30 my-machine phc2sys: [9366.913] eth0 sys offset        53
> s2 freq  -75759 delay   2000
> Aug  5 10:55:31 my-machine phc2sys: [9367.913] eth0 sys offset       -30
> s2 freq  -75826 delay   1875
> Aug  5 10:55:32 my-machine phc2sys: [9368.914] eth0 sys offset       -36
> s2 freq  -75841 delay   2001
> ...
>
> Thanks.
>