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 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.
As the paper clarifies, this is for the performance of non-atomic read/writes in sequential setting. The paper left the performance evaluation for atomic read/writes to future work. Is there any indication yet regarding the performance in a parallel setting compared to weaker guarantees?
That's right -- we first wanted to establish that existing OCaml code wouldn't be adversely impacted. There are various efforts ongoing to build interested (locked and lock-free) concurrent data structures, so that will inform the parallel performance results. Nothing published yet.
