NTP time sync issue

David_W

It looks as if you are using relatively local NTP servers to your physical location, which is good. You are using a cable modem, which can lead to high jitter, but c. 2.5ms system jitter isn't the end of the world.

Precision -22 suggests you might be using the on-processor TSC as your timing source.

Post the results of:
sysctl kern.timecounter.choice kern.timecounter.hardware
which will show the timecounter choices and weights, also the timecounter your system is currently using.

My experience of running NTP servers on bare metal FreeBSD installations is that the HPET is often a more stable timing source. If you want to give this a go, add a line to /boot/loader.conf.local that reads:
kern.timecounter.tc.HPET.quality=5000

You'll need to create /boot/loader.conf.local if it doesn't already exist. Once you've made the change, delete the ntpd.drift file (its contents are invalidated by the change of timing source) using:
pkill ntpd ; rm /var/db/ntpd.drift
then reboot. After the system has been running for at least 12 hours, re-run the command I gave in the previous post. Hopefully clk_jitter is significantly lower than the 2.9ms in your earlier output.

pfcode

@David_W:

Post the results of:sysctl kern.timecounter.choice kern.timecounter.hardware


sysctl kern.timecounter.choice kern.timecounter.hardware
kern.timecounter.choice: TSC-low(1000) ACPI-safe(850) i8254(0) HPET(950) dummy(-1000000)
kern.timecounter.hardware: TSC-low

pfcode

@David_W:

delete the ntp.drift file

you meant: ntpd.drift ? which I deleted.

David_W

@pfcode:

@David_W:

delete the ntp.drift file

you meant: ntpd.drift ? which I deleted.

That is the file I meant. I've edited the earlier post accordingly.

As I thought, your system had chosen TSC (well TSC-low, though the difference is not material here) as its timecounter. If you repeat that command having made the change I suggested to /boot/loader.conf.local, you should find the quality figure after HPET is now 5000 and that kern.timecounter.hardware is now HPET. It will be interesting to see whether that proves to have lower jitter (clk_jitter) and at least as good short-term stability (clk_wander) as TSC.

It may take 24 hours for things to settle down as ntpd had no drift file value to start from.

It is worth turning on pfSense's ntp RRD graphs in Services -> NTP, though I would strongly recommend you apply the patch in https://redmine.pfsense.org/issues/4423 first.

Harvy66

The offset spikes are correlated with changing system load.

time2.google.com seems to be going to crap.

$ ntpq -c 'rl' -wp
associd=0 status=0615 leap_none, sync_ntp, 1 event, clock_sync,
version="ntpd 4.2.8p4@1.3265-o Mon Oct 26 14:28:17 UTC 2015 (1)",
processor="amd64", system="FreeBSD/10.1-RELEASE-p24", leap=00, stratum=3,
precision=-22, rootdelay=31.673, rootdisp=42.253, refid=216.239.38.15,
reftime=da2c4aef.ab39b7b0  Mon, Dec 28 2015 17:57:35.668,
clock=da2c5259.63466f54  Mon, Dec 28 2015 18:29:13.387, peer=10249, tc=9,
mintc=3, offset=0.429836, frequency=-25.102, sys_jitter=0.149028,
clk_jitter=0.241, clk_wander=0.005
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+ra.steadfastdns.net
                 216.86.146.46    2 u  140  512  377   14.474    0.305   0.356
+rb.steadfastdns.net
                 216.86.146.46    2 u  254  512  377   14.848    0.267   0.442
-dns1.steadfast.net
                 216.86.146.46    2 u  299  512  377   15.048    0.428   0.346
+time1.google.com
                 120.249.107.194  2 u  290  512  377   24.103    0.586   0.206
-time2.google.com
                 217.167.3.118    2 u  527  512  377   34.978   -2.121   2.197
+time3.google.com
                 46.254.142.6     2 u  234  512  377   37.441    0.580   0.462
*time4.google.com
                 112.106.149.195  2 u  327  512  377   24.257    0.455   0.290

NTP.png_thumb

pfcode

@David_W:

If you repeat that command having made the change I suggested to /boot/loader.conf.local, you should find the quality figure after HPET is now 5000 and that kern.timecounter.hardware is now HPET.

It seemed no change, same as before, I did the reboot:


[2.2.6-RELEASE][root@router.home]/root: sysctl kern.timecounter.choice kern.timecounter.hardware
kern.timecounter.choice: TSC-low(1000) ACPI-safe(850) i8254(0) HPET(950) dummy(-1000000)
kern.timecounter.hardware: TSC-low

and my /boot/loader.conf.local:


ahci_load="YES"
kern.timecounter.tc.HPET.quality=5000

EDIT: just checked, the ntpd.drift was auto created again, and ntpq -c 'rl' -wp:


[2.2.6-RELEASE][root@router.home]/root: ntpq -c 'rl' -wp
associd=0 status=0615 leap_none, sync_ntp, 1 event, clock_sync,
version="ntpd 4.2.8p4@1.3265-o Mon Oct 26 14:28:17 UTC 2015 (1)",
processor="amd64", system="FreeBSD/10.1-RELEASE-p25", leap=00, stratum=2,
precision=-22, rootdelay=13.651, rootdisp=539.738, refid=206.108.0.131,
reftime=da2c62f2.f7edec27  Mon, Dec 28 2015 20:40:02.968,
clock=da2c667c.d9dcdc22  Mon, Dec 28 2015 20:55:08.851, peer=26673, tc=8,
mintc=3, offset=18.733259, frequency=14.160, sys_jitter=2.707991,
clk_jitter=4.381, clk_wander=0.158
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*ntp1.torix.ca   .PPS.            1 u  108  256  377   13.651   18.733   3.819
+ns509831.ip-167-114-101.net
                 192.95.25.79     3 u  247  256  377   38.462   21.008   2.539
+zero.gotroot.ca 30.114.5.31      2 u   45  256  377   63.321   18.919   5.488
-ntp3.torix.ca   .PPS.            1 u  250  256  377   12.037   17.734   3.188

pfcode

After 12 hours:


[2.2.6-RELEASE][root@router.home]/root: sysctl kern.timecounter.choice kern.timecounter.hardware
kern.timecounter.choice: TSC-low(1000) ACPI-safe(850) i8254(0) HPET(950) dummy(-1000000)
kern.timecounter.hardware: TSC-low

so the config: kern.timecounter.tc.HPET.quality=5000, didn't work?


[2.2.6-RELEASE][root@router.home]/root: ntpq -c 'rl' -wp
associd=0 status=0615 leap_none, sync_ntp, 1 event, clock_sync,
version="ntpd 4.2.8p4@1.3265-o Mon Oct 26 14:28:17 UTC 2015 (1)",
processor="amd64", system="FreeBSD/10.1-RELEASE-p25", leap=00, stratum=2,
precision=-22, rootdelay=13.518, rootdisp=534.552, refid=206.108.0.131,
reftime=da2d185a.f89c6a19  Tue, Dec 29 2015  9:34:02.971,
clock=da2d1b1c.a4e5378f  Tue, Dec 29 2015  9:45:48.644, peer=26673, tc=9,
mintc=3, offset=-4.883652, frequency=22.213, sys_jitter=3.014387,
clk_jitter=1.394, clk_wander=0.350
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*ntp1.torix.ca   .PPS.            1 u  176  512  377   13.518   -4.884   3.014
+ns509831.ip-167-114-101.net
                 192.95.25.79     3 u  174  512  377   37.712   -3.224   3.179
+zero.gotroot.ca 30.114.5.31      2 u  494  512  377   65.952   -2.459   2.313
+ntp3.torix.ca   .PPS.            1 u   40  512  377   15.540   -3.908   2.592

mer

Maybe you need to add "kern.timecounter.hardware=HPET" to loader.conf? that's what "man timecounters" seems to be saying.

pfcode

@mer:

Maybe you need to add "kern.timecounter.hardware=HPET" to loader.conf? that's what "man timecounters" seems to be saying.

you meant: loader.config.local?

fragged

Correct file name is 'loader.conf.local'.

mer

Yep, "loader.conf.local". Thanks for catching it.

pfcode

Tried all, but the kern.timecounter.hardware is always TSC-low, unless I ran the command:


sysctl kern.timecounter.hardware=HPET

Any hints?

pfcode

Solved by adding an entry (kern.timecounter.hardware, value: HPET) in the system->Advanced->System Tunables.

dbykov

@RonpfS I know it's an ancient thread but I googled and couldn't find existing solution to this problem.

In my case time sync issues in Windows (all those 0x800705B4 errors) were fixed by unchecking the "Enable KOD packets" option in NTP server ACL page.

Hope it could help someone.