Not sure I fully understand why David prefers to do the unaccounting at
free-time though? It feels unbalanced to me to increment when first mapped but
decrement when freed. Surely its safer to either use alloc/free or use first
map/last map?
If using alloc/free isn't there a THP constructor/destructor that prepares the
deferred list? (My memory may be failing me). Could we use that?
Additionally, if we wanted to extend (eventually) to track the number of shmem
and file mthps in additional counters, could we also account using similar folio
free-time hooks? If not, it might be an argument to account in rmap_unmap to be
consistent for all?
Again, see NR_FILE_THPS handling. No rmap over-complication please.
--
Cheers,
David / dhildenb
