Re: kern/53016: Clock not stable

[mlelstv%serpens.de@localhost (Michael van Elst)]

The following reply was made to PR kern/53016; it has been noted by GNATS.

From: mlelstv%serpens.de@localhost (Michael van Elst)
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/53016: Clock not stable 
Date: Wed, 4 Apr 2018 02:08:25 -0000 (UTC)

 kivinen%iki.fi@localhost (Tero Kivinen) writes:
 
 >ntp can keep it inside few seconds, but as the poll interval can go to
 >quite big value for ntp, it can get several seconds from real time
 >before ntp fixes it. 
 
 That's not how ntpd works. The clock is adjusted all the time by
 running it slower or faster.
 
 >Now one hour later the drift is already 2.7 seconds again.
 >----------------------------------------------------------------------
 >vielako (1:39) ~>ntpdate -q -u time1.mikes.fi
 >server 194.100.49.151, stratum 2, offset 2.789676, delay 0.02701
 > 4 Apr 01:39:45 ntpdate[16936]: step time server 194.100.49.151 offset 2.789676 sec
 
 Please check with 'ntpq -p' whether ntpd actually synchronizes to
 a time server. E.g.:
 
 % ntpq -p
      remote           refid      st t when poll reach   delay   offset  jitter
 ==============================================================================
 +time3.mikes.fi  193.166.4.57     2 u  753 1024  377   66.337    0.878   6.327
 *ptbtime3.ptb.de .PTB.            1 u  466 1024  377   28.496   -0.758   0.732
 +time.nrc.ca     132.246.11.231   2 u  559 1024  377  116.518   -0.451   4.356
 
 The '*' shows the time server that is used for synchronization, a '+'
 indicates verified backups.
 
 
 And check with 'ntptime' the adjustment of the system time. E.g.:
 
 % ntptime
 ntp_gettime() returns code 0 (OK)
   time de6eb184.e5ba3ca8  Wed, Apr  4 2018  4:05:56.897, (.897373194),
   maximum error 325351 us, estimated error 1085 us, TAI offset 0
 ntp_adjtime() returns code 0 (OK)
   modes 0x0 (),
   offset -244.122 us, frequency -1.885 ppm, interval 1 s,
   maximum error 325351 us, estimated error 1085 us,
   status 0x2001 (PLL,NANO),
   time constant 10, precision 0.001 us, tolerance 496 ppm,
 
 -- 
 -- 
                                 Michael van Elst
 Internet: mlelstv%serpens.de@localhost
                                 "A potential Snark may lurk in every tree."