Re: [gentoo-portage-dev] Re: Dynamic USE dependencies

[Rich Freeman <rich0@gentoo.org>]

On Mon, Apr 6, 2015 at 8:02 AM, Martin Vaeth <martin@mvath.de> wrote:
> My suggestion is something in between - less invasive
> (and, in particular, less time consuming)
> than your suggestion to recalculate the USE-settings
> with every emerge, but more automatic than the current state.

Keep in mind that keeping track of past decisions made by portage does
not require user-editable config files in /etc.  It just requires a
cache of some kind, much as we do with installed packages/etc.

That said, portage still has to spend time basically re-validating the
consistency of the entire system because we allow the use of overlays
and other situations that don't guarantee that portage will have some
kind of consistent pre-calculated depgraph handed to it.  If we
required all repositories to have some kind of pre-generated cache in
them and ensured that this was always up-to-date and better controlled
the kinds of dependency changes we made, then maybe there might be an
opportunity to offload some of the work to the repository level
instead of doing it on every Gentoo system.  Still, unless we banned
overlays I'm not sure how much even this would buy you, since you'd
have many of these that need to be merged somehow.

From Zac's email and other discussions in the past it seems like we're
basically committed to doing all these calculations all the time
anyway, so we shouldn't be too shy about taking advantage of them.

-- 
Rich