Re: AW: [chrony-users] chronyd: Can' Synchronize WHY ?

[Miroslav Lichvar <mlichvar@xxxxxxxxxx>]

On Tue, Sep 13, 2011 at 02:27:37PM +0000, thomas.schmid@xxxxxxxxx wrote:
> Hi Mroslav,
> > My first guess would be that your kernel doesn't really support the
> > readonly adjtime and every call cancels the previous adjustment. Can
> > you please try it again without noselect and with this patch included?
> > Again, the sourcestats output after 15 minutes should be enough.
> PC6 after running patched chronyd for ~30 mins:
>   chronyc> sourcestats
>   210 Number of sources = 3
>   Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
>   ==============================================================================
>   <WAN-IP1>                  19  10   26m      0.002      0.086   +290ns    38us
>   <WAN-IP3>                  14   8   18m      1.518      0.107  -2438us    25us
>   SU-Server3                 13  10   777    316.333     92.427   +286ms    16ms

Excellent, I assume you now don't see the frequent source switching.

I have looked in the linux git and I think I have found the cause:

http://git390.marist.edu/cgi-bin/gitweb.cgi?p=linux-2.6.git;a=commitdiff_plain;h=916c7a855174e3b53d182b97a26b2e27a29726a1

It's not that the readonly adjtime is not supported (it's actually
since 2.6.24), but it randomly sets the PLL offset. This seems to be
fixed in 2.6.28.

I'll change the condition to use it only with 2.6.28 and later.

Thanks,

-- 
Miroslav Lichvar

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