In message <20060119.141717.13771404.imp_at_bsdimp.com>, "M. Warner Losh" writes:
>In message: <E1EzgIS-00012m-00_at_mta1.cl.cam.ac.uk>
> Markus Kuhn <Markus.Kuhn_at_cl.cam.ac.uk> 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.
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Received on Thu Jan 19 2006 - 22:38:10 PST