Re: substitute derivation: also substitute grafts?

[Ricardo Wurmus <rekado@elephly.net>]

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

> Hi Ludo,
>
> On Mon, 10 Oct 2022 at 17:32, Ludovic Courtès <ludo@gnu.org> wrote:
>
>> 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.
>
> I have not done some stats, indeed. :-)
>
> The build/download or rebuild/redownload is really faster (at least
> for some R packages) than the graft part for some machines with
> spinning disks.  Well, I have been enough annoyed for some packages on
> that machine to end by systematically run the '--no-grafts' option for
> all packages. :-/

I’m not worried about grafts as such; I only think it’s a pity to have
grafts recomputed on machines on the very same network.  When I have a
direct link from one machine to another it is very fast to just copy
things over instead of performing the graft locally.

This is not something that can be decided generally.  When substituting
from a remote server it’s probably the right thing to compute the graft
locally, but there are a number of cases where that’s not a good idea
(e.g. machines on the same network, underpowered aarch64 machines
downloading substitutes from a faster machine, etc).

-- 
Ricardo