An in-depth Look at OCaml’s new “Best-fit” Garbage Collector Strategy – OCamlPro

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The Garbage Collector probably is OCaml’s greatest unsung hero. Its pragmatic approach allows us to allocate without much fear of efficiency loss. In a way, the fact that most OCaml hackers know little about it is a good sign: you want a runtime to gracefully do its job without having to mind it all the time.But as OCaml 4.10.0 has now hit the shelves, a very exciting feature is in the changelog:- #8809, #9292: Add a best-fit allocator for the major heap; still experimental, it should be much better than current allocation policies (first-fit and next-fit) for programs with large heaps, reducing both GC cost and memory usage. This new best-fit is not (yet) the default; set it explicitly with OCAMLRUNPARAM="a=2" (or Gc.set from the program). You may also want to increase the `space_overhead` parameter of the GC (a percentage, 80 by default), for example OCAMLRUNPARAM="o=85", for optimal speed. (Damien Doligez, review by Stephen Dolan, Jacques-Henri Jourdan, Xavier Leroy, Leo White)At …