[LinuxPPS] still some offset and jitter though using pps

[Nicola Berndt]

Nicola Berndt schrieb:

> Btw, things have settled down now (after half a day) to an offset of 
> 0.970 and a jitter of 0.017.

So I monitored things over the weekend and found it to behave nicely, 
values for offset and drift were always somewhere in the 0.0xy range. So 
once it has settled down my hard-/software combination can actually do a 
good ntp-job.

Still the startup problem resides: Just now I changed my timepulse from 
100 to 200 ms but still after starting up, the offset grows way over 200 
and takes very long to find its way back. This happens with and without 
driftfile. The driftfile also has a noticeably high value of almost 400 
and is being rewritten with similar high values after its deletion.

My kernel is a preembile kernel, timer_frequency is configured to 100 hz 
and I don't have a tickless system nor high resolution timer support 
enabled. I also tried the different available clocksources on the kernel 
command line but that didn't help. Strangely clocksource acpi_pm is not 
available under 
/sys/devices/clocksource/clocksource0/available_clocksource , only tsc, 
pit and jiffies.

So for now that is as much information as I can give.
What really puzzles me, ist that the system can obviously keep a stable 
and precise time. How comes, it drifts off so badly right after startig 
up and needs so long to come back? Could anyone please explain that to me?

Best regards,
./nico berndt