| Re: [chrony-dev] SW/HW timestamping on Linux |
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On Wed, Dec 07, 2016 at 04:31:38PM -0800, Denny Page wrote:
>
> > On Dec 07, 2016, at 09:20, Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:
> >
> > Yes, I think that might be helpful. I spent some time today comparing
> > your method with the current code and at least on my system with i210
> > I see a shift in the distribution of the offset to one side when the
> > network is (heavily) loaded. Compare these two histograms
> >
> > http://i.imgur.com/GsRwhyX.png (min delay * 1.1)
> > http://i.imgur.com/MHYRCCx.png (min delay + sys_prec)
>
> Can you say a bit about how these graphs were done? I would like to compare to the systems I have.
I've synchronised the system clock to the PHC with
"phc2sys -s eth0 -m -q -O 0 -N 25 -R 20", configured chronyd to not
adjust the system clock (noselect), and printed in chronyd the raw
PHC-sys offset and delay for each PHC reading.
> Have you tested any NICs other than the I210?
I've confirmed with the 82579LM card that the distribution of the
delay is sensitive to network load. I'd be surprised if it wasn't
asymmetric.
--
Miroslav Lichvar
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