I am getting the following output from the ptp4l command on a slave PTP
node. When I terminate it (with Ctrl+C), some global statistics are printed
out at the bottom, but I cannot interpret the values, as I do not find any
evident correspondences with the values in the above output. To be precise,
I know what the fields offset, min, max should be referring to in general,
but:
1. why are there pairs of values instead of single values for each of
those fields?
2. what is "dev" actually? If it's the standard deviation "of
something", what's the point in having the min and max subfields?
3. how are those pairs of values supposed to be computed or related to
the above recordings?
4. can you explain the meaning of drift, especially?
# ptp4l -p /dev/ptp0 -i eth0 -l 6 -m -s -2
ptp4l[156535.175]: selected /dev/ptp0 as PTP clock
ptp4l[156535.179]: port 1: INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[156535.181]: port 0: INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[156535.183]: version=2 ports=2
ptp4l[156535.184]: access_delay=164000
ptp4l[156535.185]: UTC offset: 37
ptp4l[156535.187]: port 1: link up
ptp4l[156536.340]: port 1: new foreign master 0010a1.fffe.9477ff-1
ptp4l[156540.354]: selected best master clock 0010a1.fffe.9477ff
ptp4l[156540.355]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE
ptp4l[156541.044]: master offset3199658 s0 freq -3906 path delay 0
ptp4l[156542.055]: master offset3199829 s3 freq -3737 path delay 0
ptp4l[156543.066]: master offset3199792 s1 freq -3737 path delay38
ptp4l[156544.077]: master offset -8 s2 freq -3739 path delay38
ptp4l[156544.078]: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
ptp4l[156545.088]: master offset-25 s2 freq -3752 path delay40
ptp4l[156546.099]: master offset-34 s2 freq -3759 path delay40
ptp4l[156547.110]: master offset-43 s2 freq -3768 path delay41
ptp4l[156548.111]: master offset-17 s2 freq -3757 path delay41
ptp4l[156549.122]: master offset-19 s2 freq -3759 path delay39
ptp4l[156550.133]: master offset-12 s2 freq -3757 path delay39
ptp4l[156551.144]: master offset -7 s2 freq -3755 path delay40
ptp4l[156552.155]: master offset-20 s2 freq -3764 path delay40
ptp4l[156553.166]: master offset -9 s2 freq -3759 path delay40
ptp4l[156554.177]: master offset-11 s2 freq -3761 path delay40
^C
ptp4l[156554.674]:
ptp4l[156554.674]: offset:
ptp4l[156554.674]: dev = 4.716450, -12.571429
ptp4l[156554.674]: min = 4.716450, 12.571429; max = 4.966555, 14.00
ptp4l[156554.674]: dev:
ptp4l[156554.675]: dev = 1.903343, 3.305985
ptp4l[156554.675]: min = 1.903343, 2.691777; max = 1.959507, 3.305985
ptp4l[156554.675]: drift:
ptp4l[156554.675]: dev = 2.623987, -3758.795853
ptp4l[156554.675]: min = 2.623987, 3758.372996; max = 2.934894, 3758.795853
ptp4l[156554.676]: avg: 12
___
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