From #2686 (reply in thread)

It looks like some change between kernel versions 6.0.16 and 6.1.6 breaks the MemoryMapper (which is enabled by default via --use-memory-manager).

Poking through a summary of changed in Linux 6.1, there seems to be a fair bit of memory management changes.

"Folio changes: this round has focused on shmem" in particular seems relevant. It looks like folios are a new way of organizing memory in the kernel, and ought to be transparent to user space, but maybe there's a bug or some subtle API change. https://www.theregister.com/2021/11/15/linux_5_16_rc1/

There's also some work on hugepages, though it looks like the application would need to opt into it. https://kernelnewbies.org/LinuxChanges#Linux_6.1.Allow_a_process_to_induce_collapsing_of_memory_into_transparent_hugepages

I'll set up a fedora 37 VM and see if I can poke around a bit. I'll see if I can create a small repro to ask the kernel folks about.