I work on Semgrep, and we have been trying to get onto OCaml 5 for quite some time (we are currently using 4.14.0). We have experienced major memory regressions when trying OCaml 5, though we are hopeful that with the reintroduction of compaction in 5.2 we will be able to tune the GC and compact judiciously in order to make the move.
Unfortunately, I’ve just discovered another issue that may be a deal breaker, since we use alarms to limit memory use and avoid crashing hard whenever possible. Happily, it has already been fixed, but it has not yet been released except in the 5.3.0 alpha. Is 5.2.1 planned, and if so, when is it expected? We’d prefer not to have to wait for 5.3.0, and we are also concerned about migrating to a fresh minor version.
Not many core compiler developers actively check this forum. May I recommend reporting issues for memory regressions at Issues · ocaml/ocaml · GitHub so that the issue gets the attention from the right set of folks?
An option if you do not want to wait is to copy-paste the implementation of the gc alarms, as it is about 15 lines and does not depend on anything else in the file (remove the call to Domain.at_exit if you do not use domains in order to make it portable across OCaml versions).
Release plans for patch-fixes version of OCaml 5.* have been quite unclear recently, for a good part because it was unclear if having a release 5.n.1 with a handful of bug fixes compared to 5.n.0 would be really stabler than the release 5.(n+1).0.
However, it seems that the 5.2 maintenance branch has accumulated quite a few import bug fixes, thus I am now planning to release 5.2.1 sometimes around the release of the beta for 5.3.0 (probably in the middle of October?).