Date: Tue, 13 Dec 2016 12:37:03 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Hrant Dadivanyan <hrant@dadivanyan.net> Cc: Ian Lepore <ian@freebsd.org>, freebsd-hackers@freebsd.org Subject: Re: system time instability Message-ID: <20161213103703.GR54029@kib.kiev.ua> In-Reply-To: <E1cGWMJ-000B5E-Mm@pandora.amnic.net> References: <20161212191832.GN54029@kib.kiev.ua> <E1cGWMJ-000B5E-Mm@pandora.amnic.net>
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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.
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