From: Jeff Hostetler Date: Thu, 19 Nov 2020 14:11:14 GMT Subject: Re: RFC: auto-enabling parallel-checkout on NFS Message-ID: In-Reply-To: <87y2ixpvos.fsf@evledraar.gmail.com> On 11/19/20 4:01 AM, Ævar Arnfjörð Bjarmason wrote: > >> The major downside is that detecting the file system type is quite >> platform-dependent, so there is no simple and portable solution. (Also, >> I'm not sure if the optimal number of workers would be the same on >> different OSes). But we decided to give it a try, so this is a >> rough prototype that would work for Linux: >> https://github.com/matheustavares/git/commit/2e2c787e2a1742fed8c35dba185b7cd208603de9 > > I'm not intrinsically opposed to hardcoding some "nr_threads = is_nfs() > ? x : y" as a stopgap. > > I do think we should be thinking about a sustainable way of doing this > sort of thing, this method of testing once and hardcoding something > isn't a good approach. > > It doesn't anticipate all sorts of different setups, e.g. in this case > NFS is not a FS, but a protocol, there's probably going to be some > implementations where parallel is much worse due to a quirk of the > implementation. > > I think integrating an optimization run with the relatively new > git-maintenance is a better way forward. > > You'd configure e.g.: > > maintenance.performanceTests.enabled=true > maintenance.performanceTests.writeConfig=true > > Which would run e.g.: > > git config --type bool core.untrackedCache $(git update-index --test-untracked-cache && echo true || echo false) > git config checkout.workers $(git maintenance--helper auto-discover-config checkout.workers) > > Such an implementation can be really basic at first, or even just punt > on the test and use your current "is it NFS?" check. > > But I think we should be moving to some helper that does the actual test > locally when asked/configured by the user, so we're not making a bunch > of guesses in advance about the size/shape of the repository, OS/nfs/fs > etc. > I kinda like this idea. It would give us a chance to let maintenance periodically probe the repo/system and improve some of these tuning knobs. Jeff