[LinuxPPS] PLL sensitivity

[Remco den Besten]

Having experience with PLLs from an electronic point of view and looking at 
the offsets of LinuxPPS, I wonder
what the time constants of this PLL are. I do not mean the 'pll time 
constant', visible with e.g. ntpdc -c kern.

I see that the frequency response of LinuxPPS in relation to the offset is 
far more sensitive than e.g. FreeBSD.
That is, I consider it to be extremely sensitive.

Being more a hardware man, I can't figure out in Rodolfo's PPSAPI mods and 
sources how the kernel is
synchronized by an external (PPS) reference, but perhaps some smoothing can 
be achieved by experimenting
with the PLL filter(s) (e.g. timing contstants) like PI-regulation 
(proportional/integral algorithms)?