| Re: [chrony-users] Hardware timestamping in CentOS 7.4 (was: Possible to get sub-millisecond accuracy?) |
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- Subject: Re: [chrony-users] Hardware timestamping in CentOS 7.4 (was: Possible to get sub-millisecond accuracy?)
- From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
- Date: Tue, 27 Jun 2017 16:24:02 +0200
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On Fri, Jun 23, 2017 at 07:10:42PM +0200, Miroslav Lichvar wrote:
> On Fri, Jun 23, 2017 at 12:11:36PM -0400, Chris Perl wrote:
> > On the one hand, moving toward the hardware removes variance from the
> > measurements. But, on the other, you're essentially ensuring that
> > you've introduced some asymmetry to the calculation (unless you have
> > the other side configured the same way).
> > So, I suppose it could be useful, if you're careful.
>
> I think we can support it, at least with a new option that would
> disable the filter. I actually have a patch in my queue to allow
> disabling the new NTP-specific filter, which should be added in 4.13
> (although there is currently no HW that supports both). I can rework
> the option to select a specific filter and allow "none", which would
> disable RX timestamping.
This is now in git. Adding "rxfilter none" to the hwtimestamp
directive should allow TX HW timestamping on NICs that support only
a PTP receive filter.
The copr repo has a fresh build from git if anyone wants to test it on
CentOS 7.
--
Miroslav Lichvar
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