Maxime Devos <maximede...@telenet.be> writes:
> [[PGP Signed Part:Undecided]] > > > On 15-09-2022 16:46, Csepp wrote: >> Ricardo Wurmus <rek...@elephly.net> writes: >> >>> [...] >>> Did I say *all items*? Well, … grafts are not included, because >>> graft >>> derivations are marked as not substitutable. >>> >>> Can we change that conditionally? I would really like to avoid >>> having >>> to build grafts on B when they have already been built on A. >> I would love this too, because IO can be incredibly slow on HDDs and >> large packages. My netbook would be thankful. >> > > There are some some opportunities for optimizations in the grafting > code before substituting more -- for example, to avoid seek times, it > would be possible to rewrite multiple files concurrently (maybe using > 'par-for-each' to process each file in a directory in parallel). > > This is already done in (guix build grafts), except that: > > * 'find-files' itself is not parallelised, even though parallelising it > could potentially reduce the time spent seeking (*) > * it uses (parallel-job-count), which is (IIUC) 1 by default because > --cores=1 by default. As grafts are more IO intensive than CPU > intensive, maybe it would be reasonable to impose a _minimum_ amount > of parallelism, I don't, know, 2 or 4 or so? > > (I'm assuming the main problem here is seek times.) > > Also combinable with the proposal of having substitutes for grafts. > > Greetings, > Maxime. > > (*) IIUC, the time for N parallel seeks should, in theory, ≃ 1 seek, > for small values of N, because of elevator algorithms. > > [2. OpenPGP public key --- application/pgp-keys; > OpenPGP_0x49E3EE22191725EE.asc]... > > [[End of PGP Signed Part]] Could we store the offsets of references somewhere at build time?
