hyc, 
There was a paper published in 2022 that was highly critical of using #mmap in a database management system. I wrote a lot about it on twitter back then, but have collected it all into a blog post now. tl;dr the paper is full of crap.
https://www.symas.com/post/are-you-sure-you-want-to-use-mmap-in-your-dbms #lmdb #dbms