I don't have access to the Zulip chat, but the other benchmarks are basically testing allocating in a hot loop. I'm not surprised that doesn't scale linearly, and it's certainly not representative of real world code I've ever written.
If you have code you wrote to achieve something and hit a wall with scaling, I'm happy to take a look.
But code primarily slowed down by pointer chasing down big maps, which is MillenialMan's complaint and fits my own experience, will absolutely be sped up linearly.
A bunch of cores sitting around waiting for the next HAMT node to come in will not interfere with each other in the slightest.
https://clojureverse.org/t/parallel-transducing-context-figh...
https://www.reddit.com/r/Clojure/comments/emylbs/any_idea_wh...
https://clojurians.zulipchat.com/#narrow/stream/151168-cloju...
https://github.com/joinr/paralleltest/issues/1
Anything in particular you're looking for?