The state of the page in 2024

My slides say 16MB. I should put those on a webpage; our humble editor has a copy in his inbox, but I guess I spoke unclearly, and the notes weren't checked against the slides for that number.

To re-run the calculation, 1GiB/4KiB * 64 is 16MiB. 1GiB/4KiB * 88 is 23MiB. 1GiB/16KiB * 144 is 9.2MiB.

To explain those numbers, we need 8bytes/page for the memdesc. An order-0 folio is estimated to be 80 bytes (need to include pfn and needs to be a multiple of 16 bytes). A higher order folio will probably be 112 bytes for extra mapcount information and the deferred split list. Plus four 8byte memdescs gets us to 144 bytes.

Hope that's helpful. Let me know if I skipped a necessary step.