Re: substitute derivation: also substitute grafts?

[Ludovic Courtès]

Hi,

zimoun <zimon.toutoune@gmail.com> skribis:

> On Wed, 05 Oct 2022 at 12:03, Ludovic Courtès <ludo@gnu.org> wrote:

[...]

>> An is it too expensive for that machine to build grafts locally?
>
> Using my old desktop from work, yes the experience is really poor;
> especially for some packages where the number of grafts is sometimes
> something, e.g., see [1] where grafting were longer than building.
>
> 1: <https://yhetil.org/guix/86wnud6db3.fsf@gmail.com>

This has to be compared with the cost of a rebuild/redownload of the
same set of packages.  Even in the worst case, grafts are faster than
that.  Now, the difference is that those grafts need to be recomputed
regularly, where the rebuild/redownload would be relatively rare.

It’s a tradeoff.  We could have machinery to help determine when to
ungraft and perhaps even automate ungrafting.

Mark H Weaver <mhw@netris.org> skribis:

> I wonder how fast grafting could be if it were rewritten in C.

I’d expect it to be I/O-bound, so maybe not that much?

Thanks,
Ludo’.