Date: Wed, 06 Apr 2005 11:13:48 +0300 From: Andriy Gapon <avg@icyb.net.ua> To: Peter Jeremy <PeterJeremy@optushome.com.au> Cc: stable@freebsd.org Subject: Re: Kernel NTP flipping between FLL and PLL modes Message-ID: <42539A3C.7070807@icyb.net.ua> In-Reply-To: <20050405193226.GB84293@cirb503493.alcatel.com.au> References: <1112365401.00269464.1112352602@10.7.7.3> <1112372627.00269546.1112361001@10.7.7.3> <1112372655.00269555.1112362202@10.7.7.3> <424D7911.8060805@icyb.net.ua> <6.2.0.14.2.20050401183743.04813c10@gid.co.uk> <42527E03.5090805@icyb.net.ua> <20050405193226.GB84293@cirb503493.alcatel.com.au>
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on 05.04.2005 22:32 Peter Jeremy said the following:
> Note that this code doesn't exist in 5.3. It was introduced sometime
> between 5.3 and 5.4. In any case, looking at the associated comments,
> this only affects the FLL/PLL loop gain.
Yes, I see that I looked in a wrong place.
> The FLL/PLL switch is set is in sys/kern/kern_ntptime.c:hardupdate()
> using:
> time_status &= ~STA_MODE;
> if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
> L_LINT(ftemp, (time_monitor << 4) / mtemp);
> L_RSHIFT(ftemp, SHIFT_FLL + 4);
> L_ADD(time_freq, ftemp);
> time_status |= STA_MODE;
> }
> and this code hasn't changed. MINSEC is 256 (which matches the comments)
> MAXSEC is either 1200 or 2048 (depending on which header file is active),
> though the comments imply it is 1024. mtime is the time since the last
> adjustment (call to hardupdate()).
MAXSEC==2048 is used, the contrib header file could not be included
because its directory is not included with -I. Besides I've verified it
by sneaking in -E
> STA_FLL is set in ntpd/ntp_loopfilter.c:
> if (sys_poll > NTP_MAXDPOLL)
> ntv.status |= STA_FLL;
> though the associated comment states "for legacy only". (And I'm
> never seeing STA_FLL transitions in syslog). This sets STA_FLL if the
> polling interval is > 2^10 (1024). By default, sys_poll is limited to
> NTP_MAXDPOLL so this should never occur. (You can over-ride it with
> "maxpoll N" on peer/server config lines).
I am using the default value of maxpoll, no overrides.
So, IMO this leaves one possibility: mtemp > 2048, i.e. hardupdate() was
not called for longer than this time i.e. either ntp_adjtime() was not
called or it was called without MOD_OFFSET.
It looks like it is not trivial to find the cause of this.
BTW, what is the best way to get out of ntpd everything it can tell
about its operations ?
--
Andriy Gapon
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