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Bug#773252: systemd-timesyncd syncs time about once per minute

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Jos van Wolput

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Dec 15, 2014, 10:50:02 PM12/15/14
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Package: systemd
Version: 215-8 and 218-1
Severity: normal

Dear Maintainer,

Systemd-timesyncd syncs time about once per 60 seconds.
I don't know if this very short interval is a bug or really intented.
Should it not be once in 60 minutes?
If this short interval is indeed intended, how could it be set to a longer value ?

-- System Information:
Debian Release: jessie/sid + experimental
Architecture: amd64 (x86_64)
Kernel: Linux debian 3.18-0 amd6
Systemd: 218-1

Kind regards,
Jos v.Wolput


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Michael Biebl

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Dec 16, 2014, 8:10:03 AM12/16/14
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Am 16.12.2014 um 04:45 schrieb Jos van Wolput:
> Package: systemd
> Version: 215-8 and 218-1
> Severity: normal
>
> Dear Maintainer,
>
> Systemd-timesyncd syncs time about once per 60 seconds.

What makes you think systemd-timesync syncs the clock once every 60 seconds?


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universe are pointed away from Earth?

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Michael Biebl

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Dec 16, 2014, 8:40:03 AM12/16/14
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Am 16.12.2014 um 14:07 schrieb Michael Biebl:
> Am 16.12.2014 um 04:45 schrieb Jos van Wolput:
>> Package: systemd
>> Version: 215-8 and 218-1
>> Severity: normal
>>
>> Dear Maintainer,
>>
>> Systemd-timesyncd syncs time about once per 60 seconds.
>
> What makes you think systemd-timesync syncs the clock once every 60 seconds?

I just studied the code and timesyncd starts with a minimal 32 second
interval (NTP_POLL_INTERVAL_MIN_SEC) which is increased until it reaches
the maximum 2048 second polling interval (NTP_POLL_INTERVAL_MAX_SEC). It
seems to use an exponential like back-off algorithm as shown by the journal

> Dez 16 14:07:41 pluto systemd-timesyncd[12409]: interval/delta/delay/jitter/drift 32s/+0.253s/0.028s/0.000s/+500ppm
> Dez 16 14:08:13 pluto systemd-timesyncd[12409]: interval/delta/delay/jitter/drift 64s/-0.005s/0.025s/0.002s/+460ppm
> Dez 16 14:09:17 pluto systemd-timesyncd[12409]: interval/delta/delay/jitter/drift 128s/-0.022s/0.040s/0.008s/+373ppm
> Dez 16 14:11:25 pluto systemd-timesyncd[12409]: interval/delta/delay/jitter/drift 128s/-0.053s/0.024s/0.050s/+165ppm
> Dez 16 14:13:33 pluto systemd-timesyncd[12409]: interval/delta/delay/jitter/drift 256s/+0.030s/0.124s/0.055s/+165ppm (ignored)
> Dez 16 14:17:50 pluto systemd-timesyncd[12409]: interval/delta/delay/jitter/drift 256s/-0.056s/0.026s/0.052s/+55ppm
> Dez 16 14:22:06 pluto systemd-timesyncd[12409]: interval/delta/delay/jitter/drift 512s/-0.012s/0.025s/0.050s/+43ppm
> Dez 16 14:30:38 pluto systemd-timesyncd[12409]: interval/delta/delay/jitter/drift 1024s/+0.046s/0.149s/0.059s/+43ppm (ignored)

roughly 30s -> 1m, 1m -> 2m, 2m -> 4m, 4m -> 8m ...

This looks like a sensible approach to me.
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Jos van Wolput

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Dec 16, 2014, 8:50:03 AM12/16/14
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On 12/16/2014 09:07 PM, Michael Biebl wrote:
>
> What makes you think systemd-timesync syncs the clock once every 60 seconds?
>
Even every 32 seconds!
The systemd journal and the output of systemctl status systemd-timesyncd.service:

systemd-timesyncd.service - Network Time Synchronization
Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; disabled)
Active: active (running) since Tue, 16 Dec 2014 21:21:56 +0800; 8min ago
Docs: man:systemd-timesyncd.service(8)
Main PID: 24099 (systemd-timesyn)
Status: "Using Time Server 202.112.10.36:123 (0.debian.pool.ntp.org)."

Dec 16 21:24:42 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 64s/+0.030s/0.192s/0.043s/+500ppm
Dec 16 21:25:47 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.194s/0.095s/0.154s/+500ppm
Dec 16 21:26:19 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.084s/0.111s/0.142s/+500ppm
Dec 16 21:26:51 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.060s/0.098s/0.132s/+500ppm
Dec 16 21:27:23 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.066s/0.101s/0.134s/+500ppm
Dec 16 21:27:56 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.063s/0.095s/0.133s/+500ppm
Dec 16 21:28:28 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.058s/0.081s/0.053s/+500ppm
Dec 16 21:29:00 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.075s/0.100s/0.054s/+500ppm
Dec 16 21:29:32 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.087s/0.133s/0.054s/+500ppm
Dec 16 21:30:05 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.126s/0.088s/0.030s/+500ppm

Jos van Wolput

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Dec 16, 2014, 9:20:03 AM12/16/14
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After half an hour I stll get an interval of 32. it doesn't increase exponentialy:

Dec 16 21:24:42 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 64s/+0.030s/0.192s/0.043s/+500ppm
Dec 16 21:25:47 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.194s/0.095s/0.154s/+500ppm
Dec 16 21:26:19 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.084s/0.111s/0.142s/+500ppm
.....
Dec 16 22:01:01 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.065s/0.116s/0.018s/+500ppm
Dec 16 22:01:33 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.065s/0.110s/0.017s/+500ppm
Dec 16 22:02:05 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.062s/0.104s/0.015s/+500ppm
Dec 16 22:02:38 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.062s/0.097s/0.005s/+500ppm
Dec 16 22:03:10 debian systemd-timesyncd[24099]: interval/delta/delay/jitter/drift 32s/+0.110s/0.097s/0.019s/+500ppm

Jos van Wolput

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Dec 20, 2014, 1:00:03 AM12/20/14
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On 12/16/2014 09:31 PM, Michael Biebl wrote:
>
> roughly 30s -> 1m, 1m -> 2m, 2m -> 4m, 4m -> 8m ...
>
> This looks like a sensible approach to me.
>

As the interval of systemd-timesyncd on my system never increases I have disabled systemd-timesyncd
and instead inabled ntp service (/etc/init.d/ntp).

Jos van Wolput

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Dec 21, 2014, 2:40:03 AM12/21/14
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This issue is fixed by enabling hpet in grub, setting GRUB_CMDLINE_LINUX="upgrade-from-grub-legacy vga=769 hpet=enable".
Using htep as clocksource instead of acpi_pm the interval now increases exponentially:

Dec 21 14:27:26 debian systemd-timesyncd[2663]: Using NTP server 202.112.29.82:123 (0.cn.pool.ntp.org).
Dec 21 14:27:26 debian systemd-timesyncd[2663]: interval/delta/delay/jitter/drift 32s/-0.083s/0.045s/0.000s/-411ppm
Dec 21 14:27:58 debian systemd-timesyncd[2663]: interval/delta/delay/jitter/drift 64s/+0.014s/0.044s/0.005s/-299ppm
Dec 21 14:29:02 debian systemd-timesyncd[2663]: interval/delta/delay/jitter/drift 128s/+0.020s/0.046s/0.013s/-222ppm
Dec 21 14:31:43 debian systemd-timesyncd[2663]: interval/delta/delay/jitter/drift 256s/+0.042s/0.048s/0.016s/-140ppm
Dec 21 14:35:59 debian systemd-timesyncd[2663]: interval/delta/delay/jitter/drift 512s/+0.041s/0.049s/0.018s/-100ppm
Dec 21 14:45:03 debian systemd-timesyncd[2663]: interval/delta/delay/jitter/drift 512s/+0.066s/0.049s/0.026s/-35ppm
Dec 21 14:54:08 debian systemd-timesyncd[2663]: interval/delta/delay/jitter/drift 1024s/+0.025s/0.044s/0.023s/-23ppm
Dec 21 15:11:44 debian systemd-timesyncd[2663]: interval/delta/delay/jitter/drift 2048s/+0.038s/0.046s/0.021s/-14ppm

Jos van Wolput

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Dec 21, 2014, 2:50:02 AM12/21/14
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This issue is fixed by enabling hpet in GRUB_CMDLINE_LINUX="upgrade-from-grub-legacy vga=769 hpet=enable".
By default hpet is disabled.
Using hpet instead of acpi_pm as clocksource the interval now increases exponentially:
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