Kernel time-keeping adjustments - how to tune?
john at starfire.mn.org
Mon Jan 17 13:12:49 PST 2005
On Mon, Jan 17, 2005 at 03:05:22PM -0600, Kevin Kinsey wrote:
> John wrote:
> >OK - on my FreeBSD 5.3-STABLE system, as I have documented (cf:
> >message thread Re: ntpd problems since upgrading to 5.3), ntpd
> >won't run, even with an identical configuation to the 5.2.1 system
> >next to it. Furthermore, when I run adjkerntz -a, it totally whacks
> >the system's ability to keep time - it races forward at quite a
> >high rate. ntpdate runs, and sets the time correctly.
> >At one point, something managed to get the timekeeping parameters
> >pretty near normal - less than a second of drift per hour (much
> >better than the 40% rate it is now - it gains about 24 seconds PER
> >MINUTE). Then I ran adjkerntz -a again, just to see if it really
> >was the culprit. It does seem that it is adjkerntz that is causing
> >(or triggering) the problem, but now I can't get the system back
> >to a decent time-keeping rate. Whatever it was I stumbled across
> >before, I'm not finding it again now.
> >Now, it doesn't appear that adjkerntz itself has changed in YEARS,
> >so it must be some change in the system call operation, parameters,
> >or data structures that is causing this.
> >So - since I don't seem to be able to stumble across what I did
> >right before to get the timekeeping somewhat near normal, I am
> >wondering if there's a manual way to reach them.
> I read through the cited thread, and don't see any replies;
> nor do I see enough explanation to give you any magic
> beans. Of course, I'm no one's fairy godmother...
LOL! No - I don't expect you to be - that'd take ALL the challenge
out of it!
> > the clock on my 5.3-STABLE system is RACING.
> > It is going at almost twice as fast as real time.
> Hmm, that might mean something. What do you get from:
> sysctl -a | grep timecounter
I don't know what all this means, but here it is...
kern.timecounter.choice: TSC(800) i8254(0) dummy(-1000000)
Are these all documented somewhere? I'm sure they must be, but
I don't know where to look...
> IANAE, but I wonder if ntpd is going to be able to sync
Well, maybe you will be soon. An "expert" is anyone who makes
three consecutive correct guesses on the same topic... :)
> up until the local clock runs realistically....
Well, I thought of that, too, and during the period between when I
had it running decently and before I decided to try (all too
successfully) to recreate the problem with adjkerntz, I did
try ntpd again, but with the same results. It simply acted like
it could not see the server.
> Kevin Kinsey
john at starfire.MN.ORG
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