Mmap has the ability to use large page sizes to improve performance. (The default page size is 4KiB, an artifact of the 386 days). It is possible to increase page sizes to at least 2MiB:

https://stackoverflow.com/questions/32336694/huge-pages-on-mac-os-x

It would be worth investigating these flags to see if the larger page sizes improve our memory paging throughput.