Almost no languages with gc have shared-memory parallelism. Supposedly they managed to add it to ocaml and it will be merged some time in 2019. .net languages and java also support it, along with haskell. I don't know of any lisps or schemes that do, neither does python, ruby, js, or any other popular language that doesn't do manual memory management.
Ocaml's problems are elsewhere, it's extremely verbose and completely fragmented (there are 3 competing standard libraries, 3 competing macro systems, 2 competing repls, and it never ends). It's very fast and its gc is really good but it's a pain in the ass to write anything non-trivial in it.