[LinuxPPS] ns decreasing on update

[Jeff Angielski]

Marc Leclerc wrote:
> Hi,
> 
> Something looks weird to me here, my trace coming from the interrupt has
> the nano second decreasing on interrupt entry, wondering why this is
> happening.

Assuming your PPS is accurate, you are seeing the error in your system 
clock as well as jitter due to the time it takes to service and interrupt.

If you have not configured your kernel with the "low latency desktop" 
preemption model (CONFIG_PREEMPT), you should go back and do so.  That 
should reduce the interrupt jitter to the lowest it's going to get.

Then it's up to you to figure out why your system clock is slow or fast...

-- 
Jeff Angielski
The PTR Group
www.theptrgroup.com