| Re: [chrony-dev] SW/HW timestamping on Linux |
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On Wed, Nov 23, 2016 at 03:24:56PM -0800, Denny Page wrote:
> I am now seeing better standard deviations with hardware timestamping than software timestamping. Thank you.
>
> Couple of caveats:
> - I need to disable priority scheduling (-P). With priority scheduling, software stamps still have lower stddev.
> - I can only use a single ethernet interface. With multiple interfaces, software stamps still have lower stddev.
That's interesting. Were you testing this with the patch that ignores
non-HW measurements and did any of these two things change probability
of getting a 'D H' measurement?
FWIW, I tried running chronyd with -P 50 for a bit and I didn't notice
any changes.
> I am still seeing issue strange offset issues.
> 210 Number of sources = 3
> Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev
> ==============================================================================
> 192.168.230.240 16 8 15 +0.002 0.009 +24ns 45ns
> 192.168.230.244 22 9 21 -0.002 0.007 -25ns 48ns
> 192.168.230.2 16 7 53 -0.004 0.003 +12us 45ns
>
>
> Both crony instances think the other is off by a large amount. This disagreement is very stable.
That suggests the interleaved mode is not working. Are the peers
specified with the xleave option? If HW timestamping is otherwise
working, an offset of 12 microseconds tells us that the daemon TX
timestamps of the peer have an error of 24 microseconds.
--
Miroslav Lichvar
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