Kernel PLL graphs
Matthew.Selsky at twosigma.com
Wed Aug 3 21:49:41 UTC 2016
On Wed, Aug 03, 2016 at 02:24:01PM -0700, Hal Murray wrote:
> Time to make sure I've got the right number of negatives... "I have !NO_HZ
> set" means you have unset NO_HZ which probably means you had to build your
> own kernel.
We build our own kernels and we boot our stratum 1 clocks with "nohz=off"
> Do you have flag3 turned on? If so, the kernel does all the work and maxpoll
> is essentially ignored.
We do not have flag3 turned on. ntpd is reading the GPS via shared memory. The GPS comes with a lightweight daemon that reads /dev/refclock0 and stuffs the time in shared memory.
> I though there was a min to maxpoll so I'm a bit surprised you could set it
> to 1.
We had a local patch to change the minimum value of minpoll/maxpoll to 1. Eric recently committed a similar patch upstream. https://gitlab.com/NTPsec/ntpsec/commit/a3047c7a375877436d422e04a138aace7ce1bd06
> At least for the effect I'm discussing, it only matters if you have a PPS.
We're using PCIe GPS receiver cards.
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