Date: Sun, 21 Feb 2010 10:02:21 +0100 From: Torfinn Ingolfsen <torfinn.ingolfsen@broadpark.no> To: freebsd-stable@freebsd.org Subject: Re: ntpd struggling to keep up - how to fix? Message-ID: <20100221100221.e6809b9e.torfinn.ingolfsen@broadpark.no> In-Reply-To: <20100221050823.GB22670@server.vk2pj.dyndns.org> References: <20100212132947.eb2af3d0.torfinn.ingolfsen@broadpark.no> <20100212131117.GA51905@icarus.home.lan> <20100212174452.2140cd72.torfinn.ingolfsen@broadpark.no> <20100217194927.e3ec60ae.torfinn.ingolfsen@broadpark.no> <20100217200322.da66c9f8.torfinn.ingolfsen@broadpark.no> <20100218205458.GA78560@server.vk2pj.dyndns.org> <20100218231223.ec6b9fa8.torfinn.ingolfsen@broadpark.no> <20100219003844.acdaa866.torfinn.ingolfsen@broadpark.no> <20100220015351.GB81639@server.vk2pj.dyndns.org> <20100220223201.178e67dd.torfinn.ingolfsen@broadpark.no> <20100221050823.GB22670@server.vk2pj.dyndns.org>
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On Sun, 21 Feb 2010 16:08:23 +1100 Peter Jeremy <peterjeremy@acm.org> wrote: > That's definitely not good - though it's marginally better than before. > I have checked on a local machine and the timecounter frequency definitely > needs to be adjusted in the opposite direction to the ntpd drift. > > I think I see the problem: I suggested 3579545Hz - 2500ppm, which > gives an ACPI frequency of 3570596Hz. There was some miscommunication > and you have set an ACPI frequency of 3577045Hz which is 2500Hz (or > 698ppm) lower. The drift reported by the time resets has gone from > +1930ppm (14.5s in 2:05:17) to +1233ppm (8.4s in 2:20:06) - which is > 697ppm - fairly close to the change you made. (The PLL is running > at +500ppm so the actual clock offset is 500ppm more than the "time > reset" reports suggest. Very good info, it helps me understand more. Thanks! > Having re-checked my maths, using both your "time reset" results, can > you please try: > sysctl machdep.acpi_timer_freq=3570847 Ok, trying that now: root@kg-f2# sysctl machdep.acpi_timer_freq=3570847 machdep.acpi_timer_freq: 3577045 -> 3570847 root@kg-f2# /etc/rc.d/ntpd stop Stopping ntpd. root@kg-f2# rm /var/db/ntpd.drift root@kg-f2# /etc/rc.d/ntpd start Starting ntpd. > That should result in a drift of close to zero (well within NTP's > lock range of +/- 300ppm). Good. > No. Once ntpd decides to continuously step, something is broken. Aha, very good to know. -- Torfinn
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