[LEAPSECS] leap second festivities?

[Miroslav Lichvar]

On Wed, Jul 01, 2015 at 11:39:47AM +0000, Poul-Henning Kamp wrote:
> They dropped the raised-cosine thing, because the change of frequency
> was bad for the NTP clients PLL's.
> 
> The linear smear is just a slightly different frequency for a fixed
> period of time, that's a lot easier for the PLL to track.

A frequency step of ~14 ppm is easier to follow than a gradual change?
That doesn't sound right to me, at least not with the standard NTP
PLL/FLL loop.

I actually have some data from experiments I did when was I implementing
a server smear in chrony. Here you can see the offset of ntpd
synchronized with a server using a cosine function and a server
using a linear function over the same interval.

https://mlichvar.fedorapeople.org/tmp/leap/cos_lin_smear.png

The maximum offset with the linear smear was almost three times larger
than with the cosine smear. I think there is a different reason why
they switched to the linear smear.

-- 
Miroslav Lichvar