Yo Matthew! On Mon, 6 Feb 2017 14:30:43 -0500 Matthew Selsky <matthew.sel...@twosigma.com> wrote:
> Does the shm driver need any modifications?
> # ntpshmmon
> ntpshmmon version 1
> # Name Seen@ Clock Real L
> Prec
> sample NTP0 1486408132.108158719 1486408132.107249611 1486408132.107249498 0
> -20
> sample NTP0 1486408133.108366587 1486408133.107396038 1486408133.107395887 0
> -20
> My GPS card comes with a daemon that writes to SHM and it looks like
> it has nanosecond precision.
Yeah, that looks good.
> And maybe the card's daemon needs to be updated to change -20 to -30?
AFAIK ntpd does not use refclock precision. At least I could not find it.
The only place I can see that precision is used is in ntpd/ntp_proto.c
where is it part of the computation of 'Root Distance (LAMBDA)'.
That calc is in ntp_proto.c in root_dispersion(). Which is NOT called
for refclocks:
if (!(peer->flags & FLAG_REFCLOCK) && root_distance(peer) >=
OTOH, prolly best to set it to -30, just for grins. Someday it might
matter, or I might have missed something, or just to seem to do the
right thing.
RGDS
GARY
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