I believe the less scary race in Java implies a lower performance upper bound. Does the nicer guarantees in multicore OCaml have the same drawback? I.e. even less than Java?
The details of the 'LDRF' (local data race freedom) property are described in detail here: https://anil.recoil.org/papers/2018-pldi-memorymodel.pdf
The performance numbers are in the paper abstract: "our evaluation demonstrates that it is possible to balance a comprehensible memory model with a reasonable (no overhead on x86, ~0.6% on ARM) sequential performance trade-off in a mainstream programming language". It's a little higher on PowerPC but still very usable, and RISC-V overheads should be roughly comparable to ARM.