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Re: [Gnu-arch-users] the state of the union
From: |
Andrew Suffield |
Subject: |
Re: [Gnu-arch-users] the state of the union |
Date: |
Wed, 18 Aug 2004 18:31:46 +0100 |
User-agent: |
Mutt/1.5.6+20040803i |
On Wed, Aug 18, 2004 at 10:23:40AM -0700, Tom Lord wrote:
> > > That strikes me as a "noop" (no new structure) rearrangement of what's
> > > already there. It's an entertaining rearrangement since it makes the
> > > layout of a changeset tree a little more intuitive and navigable for
> > > humans.... but it doesn't really change anything other than that.
>
> > Well, it does have some different performance characteristics -
> > partial changeset application is more efficient this way, as you can
> > fetch precisely the components you need. But that's coincidental (and
> > assumes it's not been stuffed in a tarball). The important point is
> > that it simplifies code that follows the above model, since it maps
> > more or less directly to the desired in-core data structure.
>
> Changesets are tiny. You can compute a gazillion different views of
> them before you notice a performance hit.
I'm not betting on them remaining that way. There's no particular
reason why they *should* be tiny in general - summary deltas in
particular will tend to grow in step with the interval of time they
summarise. A changeset from linux 2.4.0 to 2.6.0 is going to be
*huge*, and it's reasonable to say that we should be able to partially
apply it.
That's a completely different discussion, though. I've got a small
sackful of performance issues with changesets that can (and should) be
reasonably easily fixed.
> > > In all seriousness: on the same principles, perhaps the changeset
> > > format should expand so that you can also drop in .html files of
> > > "annotation" about the various changes enclosed?
>
> > (I'm ignoring this for now because I don't have the faintest idea, and
> > don't have time to think it through).
>
> (I was and slightly still am confused about whether you are talking
> about an API for changesets or the changeset disk format.
Somewhere between the two. There shouldn't be a huge difference. I'm
thinking in general principles, rather than any particularly firm
plans.
> If the
> disk format, and if you want to make an isomorphic change, there being
> precious little performance incentive for such changes, presumably the
> reason is to make the changesets more human-navigable.
"Yes", but I'm primarily thinking about "humans that are writing
programs to manipulate changesets". It just happens to be better for
the others at the same time.
I expect we *can* arrange things so that's they're more easily
navigated in raw form, though.
> By extension,
> allowing in arbitrary annotation would also make sense.)
Allowing arbitrary *anything* would make sense really (one tool should
be able to inject its own private metadata into a changeset, and have
it come out again at the other end), but that's not directly
relevant. It's a relatively minor detail for when we're ready to
actually design the pesky thing.
--
.''`. ** Debian GNU/Linux ** | Andrew Suffield
: :' : http://www.debian.org/ |
`. `' |
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[Gnu-arch-users] Re: the state of the union, Miles Bader, 2004/08/17
Re: [Gnu-arch-users] the state of the union, Greg Hudson, 2004/08/18
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