Dune 3.0 performance · Dune devs & users

I feel as though dune 3.0.3 is thinking a little to long when I am building Coq. For instance, after finishing dune build for the master Coq repo, and running dune build again, it takes a couple of seconds to realize that nothing needs to be done. @Rudi Grinberg are you are aware of similar issues? What is the best way to submit such a bug report?

Rudi Grinberg (Mar 31 2022 at 18:05):

Can you confirm that the situation is better in 2.9.x?

Ali Caglayan (Mar 31 2022 at 18:08):

Trying it now, it needs to rebuild the whole thing unfortunately due to the different OCaml version

Rudi Grinberg (Mar 31 2022 at 18:08):

Usually, these issues pop up from changes in the build rules rather than dune itself. We are quite sensitive to performance regressions since they are felt very acutely by the JST people.

Ali Caglayan (Mar 31 2022 at 18:14):

Hmm it actually looks like it is a little faster

Ali Caglayan (Mar 31 2022 at 18:15):

I think the main difference is that dune 3.0 is actually reporting what it is doing where dune 2.9 wouldn't say anything.

Ali Caglayan (Mar 31 2022 at 18:15):

So looks like my initial feeling is incorrect.

Ali Caglayan (Mar 31 2022 at 18:19):

I did observe some job number bottlenecks however when rebuilding a project. I had dune build in watch mode and sometimes it would get stuck with one job. When I restarted the watch process it went back to multiple jobs.