| Re: [chrony-dev] Let the kernel write the sys clock to RTC |
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On Wed, 19 May 2010, Miroslav Lichvar wrote:
On Wed, May 19, 2010 at 10:00:09AM -0400, Piotr Grudzinski wrote:
Interesting.
For me, 1.24 settles down to the same drift, and I can't imagine what
could be causing this.
What system are you using for testing? Mine is a small 192MHz ARM 9
based board. Kernel HZ is 100.
Mine is a full size x86_64 PC, currently running kernel 2.6.33.3
compiled with CONFIG_NOHZ.
I ran ntpd program all night and this morning the estimated drift is 3.740.
And it seems that the +- convention is opposite in chrony and ntpd. So the
git chrony and ntpd seems to quite close.
I presume you have the rtcsync option enabled, maybe it somehow
affects the system clock? Does it change when it's disabled? For me,
the result is always the same.
As he says, it might be an idea to remove the rtcsync option, and see which rate
it converges to. Note that the 27 rate had a huge error associated with it.
It, the offsets seem to have been scattered all over the place. Have a look at
the output of the /var/log/chrony/measurements.log, and see what the offset
measurements look like, and also the statistics.log file to see how many
points chrony is keeping in trying to produce a fit through the data points.
Also, for chrony and adjtimex, offset is always 0 and timeconstant is 2;
for ntpd - offset is not 0 and timeconstant goes from 2 (on start) to 10.
That's ok, chrony doesn't use the kernel PLL discipline.
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