system time instability
Konstantin Belousov
kostikbel at gmail.com
Tue Dec 13 10:37:28 UTC 2016
On Mon, Dec 12, 2016 at 11:33:59PM +0400, Hrant Dadivanyan wrote:
> > On Mon, Dec 12, 2016 at 11:04:08PM +0400, Hrant Dadivanyan wrote:
> > > Now, when you ask, I start to suspect PPS delivery to uart again - cable
> > > and amplifier, but can't understand how the 100ppm error fits into that.
> >
> > If you disable PPS sync in ntp config, does the machine keep time adequately ?
> >
>
> Thanks for reminding - yes, I've tried this as well, the issue persists.
> So uart shouldn't be in charge.
>
> > There might be relatively long pauses when system management mode handlers
> > do something in response to hw events. E.g. if you have USB emulation of
> > AT keyboard enabled in BIOS, try to disable that. And update the BIOS.
>
> The USB is switched off in the BIOS. I've removed all changes in sysctl.conf
> and nice flag from ntpd, recompiled kernel as following:
> include GENERIC
> options PPS_SYNC
> device pf
> device pflog
> and started over. Dmesg is attached.
>
Please show verbose dmesg.
> CPU: Intel(R) Core(TM)2 Duo CPU E4500 @ 2.20GHz (2194.55-MHz K8-class CPU)
This is relatively old CPU which is known to have some (minor) issues with
interaction between power saving and cores. Try the following OS config:
disable deep C states, allow only C1 (there might be some tweaks in BIOS,
if possible, disable the Cn, n > 1, there too);
use LAPIC for event timer (not HPET);
re-check that you use RDTSC for the timecounter;
do not enable powerd.
You might also try the stable/11 kernel, which has more changes WRT C-states
handling and PPS/ntp locking.
More information about the freebsd-hackers
mailing list