On Sat, Nov 09, 2019 at 06:40:56PM +0100, Ludovic Courtès wrote: > Like I wrote, it’s not that simple (we’d first need the daemon to > distinguish substitution jobs from other jobs, but note that there are > also “downloads” that are actually derivation builds), and it’s not > clear to me that it’s overall beneficial anyway: it’s not supposed to be > faster to download 10 things in parallel from ci.guix.gnu.org, than to > download them sequentially.
Parallel downloading is not faster in terms of overall transfer rate from ci.guix.gnu.org. However, installing things with Guix involves downloading a lot of very small files like derivations, and Guix spends a lot of time initiating these downloads. For example, I can download things at 100 megabits, but when Guix needs to sequentially download 50 10-kilobyte files, it may take an entire minute. So there is a huge speedup with parallel downloading.
