Re: [chrony-users] gpsd, pps and chrony

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On Wed, Apr 06, 2011 at 07:18:24PM +0100, Ed W wrote:
> - I see a clear connection between my cpu Mhz as reported in say
> /proc/cpuinfo (unknown if this source is reliable when processor
> powersave in use?) and the stable chrony tracking parameters

At least here, MHz in /proc/cpuinfo is affected by powersaving and it
is a nicely rounded value, not what kernel prints in dmesg.

> I'm quite surprised that others don't see this gross variation that I
> do?  For me at least I get no value at all from chrony's saved tracking
> params because chrony is tracking an average offset of around 130ppm,
> but the bootup variation is some 100+ ppm around that offset?  Do others
> get less variation with each boot?

I just made a test with a 2.6.38-rc0 kernel and I have good
news for you :). I noticed this in dmesg:

Detected 3192.489 MHz processor.
Refined TSC clocksource calibration: 3191.999 MHz

The second value didn't change after reboot and chrony's drift stayed
the same too!

It seems to be this commit, merged just few months ago.
http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git;a=commitdiff;h=08ec0c58fb8a05d3191d5cb6f5d6f81adb419798

-- 
Miroslav Lichvar

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