# Dk builds with relocatable OCaml **URL:** \ **Category:** Ecosystem\ **Tags:** dk\ **Created:** [September 18, 2026, 11:15pm UTC](https://discuss.ocaml.org/t/dk-builds-with-relocatable-ocaml/18548 "2026-09-18T23:15:48Z")\ **Posts on this page:** 1\ **Showing post:** 1
**Author:** ![jbeckford](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/jbeckford/32/3027_2.png) [@jbeckford](https://discuss.ocaml.org/u/jbeckford)\ **Post date:** [September 18, 2026, 11:15pm UTC](https://discuss.ocaml.org/t/dk-builds-with-relocatable-ocaml/18548/1 "2026-09-18T23:15:48Z")
I thought this might be good to share with others. I had Windows builds of my build system (“dk”) failing because they were taking 2 hours to run (2hr time limit on public GitLab CI). The build is just regular opam with dune. With separate jobs to prepare a cache, I could bring it just under 2 hours. But I really didn’t like how brittle and hacky that solution was. So I decided to use the distributed caching feature of dk to bootstrap the building of dk. And now that I’ve scripted enough opam / dune / ocamlbuild / relocatable OCaml functionality into dk build rules (_package: CommonsLang\_OCaml_), I think it could be useful to some opam package maintainers. I picked `ocamlearlybird` as my representative package for no reasons other than I had used it before and it seemed representative of the size of “normal” OCaml projects. It is on GitHub so setup-ocaml is available. - 13 m 56 s to build `ocamlearlybird.exe` on GitHub windows-latest (2 vCPUs with 8 GB of RAM) the first time, but faster at 10 m 50 s after setup-ocaml initializes the cache. _For CI, 10 m 50 s is the relevant number; for desktops, 13 m 56 s is._ - 8 m 48 s to build from scratch after running my adoption build rules (_module: `CommonsLang_OCaml.Dk.OpamLock.Adopt@1.1.14`_). That performance isn’t very impressive for a binary cache, but that was only caching a few special packages like Dune and the relocatable OCaml compiler. _This is the quick-setup branch in the website below_ - 2 m 18 s to build from scratch after we’ve also created GitHub release jobs to store intermediate build artifacts. dk can “restore” from one or more GitHub releases and use them as caches: each release has zip files, and dk knows how to use HTTP Range requests to somewhat efficiently get intermediate build artifacts (ex. binary opam packages, the relocatable OCaml compiler). _This is the high-performance branch in the website below_ Net: If OCaml package maintainers adopted and created these dk-based GitHub releases, then regular OCaml users could access a loose federation of binary caches on their desktops or in CI. Net Net: I’d love to see if dk can take a stab at lowering the cost curve for AI. Today’s AI is very much like opam today: source in + artifacts out, with no sharing of artifacts. But share artifacts and the cost/waste/time/complexity goes down. AI Provenance: The dk packages (ex. CommonsLang\_OCaml) have been 100% AI generated and maintained since June 2026, and “dk” itself was hand built but AI assisted since June 2026. Caveats: I haven’t really tested out macOS and Linux in a long time, but they are in CI. Actually, for my own safety, most of my testing on Windows is in Windows CI to avoid AI badness. And I didn’t realize until too late that `ocamlearlybird` wasn’t available for OCaml 5.5 (the first conventional relocatable version), so I have mostly tested with relocatable-patched OCaml 4.14. And I haven’t yet separated MSVC packages from MinGW on Windows; you may need Visual Studio on Windows. _Expect bugs!_ Thanks: @dra27 for spending years getting relocatable OCaml working! Apology in advance: I think this has some overlap with dune pkg. But I’m on Windows and haven’t tried it out. Links: - [https://jonahbeckford.github.io/ocamlearlybird/](https://jonahbeckford.github.io/ocamlearlybird/) (mini website with performance measurements, how to adopt) - [https://diskuv.com/dk/](https://diskuv.com/dk/) (the fine details of the build system; not required for this discuss post) --- _[View the full topic](https://discuss.ocaml.org/t/dk-builds-with-relocatable-ocaml/18548)._