[AFS3-std] Re: A call for consensus on draft-deason-afs3-type-time-02

[Andrew Deason]

On Mon, 1 Aug 2011 13:32:46 -0400
Derrick Brashear <shadow@gmail.com> wrote:

> On Mon, Aug 1, 2011 at 1:28 PM, Andrew Deason <adeason@sinenomine.net> wrote:
> 
> >> b) the granularity
> >
> > This one I still have no idea on. I see reasons for both sides.
> 
> So is there a reason an extended union with the various stamp
> granularities would be a nonstarter? In particular I'd suggest the
> draft strongly discourage
> sending a larger timestamp than actual information supports (e.g.
> don't use bits to send precision you don't have, rather than
> trailing-zero-padding a
> larger than needed number)

Well, the objection to just having 64-bit seconds and 32-bit nanoseconds
is "space", and a union tag is an extra 32 bits... If we had a "100 NS
granularity" tag, then we'd have 100-ns granularity in 96 bits, whereas
now we could have 1-ns granularity in 96 bits. Unless there's some other
scheme you're thinking of that somehow makes this more efficient?

I had some kind of variable-length scheme that encoded the granularity
in the 'unused' bits of the value for coarser granularities, but I'm
pretty sure that only saved space for the *TimeRes types, and doesn't
really help for 'plain' times.

-- 
Andrew Deason
adeason@sinenomine.net