Re: [LEAPSECS] Internet-Draft on UTC-SLS

From: Poul-Henning Kamp <>
Date: Fri, 20 Jan 2006 07:27:50 +0100

In message <>, "M. Warner Losh" writes:
>In message: <>
> Markus Kuhn <> writes:
>: "M. Warner Losh" wrote on 2006-01-19 19:20 UTC:
>: > Effectively, you'd have to have two time scales in the kernel. UTC
>: > and UTC-SLS. You make it sound simple, but the hair in doing this may
>: > be quite difficult. There's more book for the kernel to keep, and it
>: > would have to expose the bookkeeping to userland for ntp to work.
>: > What makes this hard is that ntpd may introduce steers into the normal
>: > system time at normal times which it doesn't want to confuse with the
>: > steers in frequency that are used during a UTC-SLS operation.
>: You correctly point out some of the design considerations that have to
>: go into such code. You describe roughly one of the (several) different
>: ways of implementing all this that I have in mind. In comparison to how
>: complicated the Mills kernel PLL is already today, that does not
>: actually sound like an overwhelming additional complexity. Actually, it
>: sounds quite doable when you think through it a bit. Not trivial, but
>: carefully doable without performance penalty.
>Anything that makes the Mills' kernel PLL more complicated is unlikely
>to be implemented correctly.

Actually the Mills PLL isn't implemented correctly in the first place,

The fact that the design is pretty baroque doesn't help.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk_at_FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Received on Thu Jan 19 2006 - 22:38:10 PST

This archive was generated by hypermail 2.3.0 : Sat Sep 04 2010 - 09:44:55 PDT