On Wed, Aug 16, 2023 at 12:12:44PM +0200, David Hildenbrand wrote: > On 16.08.23 05:14, Matthew Wilcox wrote: > > > * Are managed on the LRU > > > > I think this is the best one to go with. Either that or "managed by > > rmap". That excludes compoud pages which are allocated from vmalloc() > > (which can be mmaped), page tables, slab, etc. It includes both file > > and anon folios. > > > > I have a handy taxonomy here: https://kernelnewbies.org/MemoryTypes > > > > Unfortunately, folio_test_lru() already exists and means something > > different ("Is this folio on an LRU list"). I fear folio_test_rmap() > > would have a similar confusion -- "Is this folio currently findable by > > rmap", or some such. folio_test_rmappable()? > But what about hugetlb, they are also remappable? We could have > folio_test_rmappable(), but that would then also better include hugetlb ... We could do that! Have both hugetlb & huge_memory.c set the rmappable flag. We'd still know which destructor to call because hugetlb also sets the hugetlb flag. > Starting at the link you provided, I guess "vmalloc" and "net pool" would > not fall under that category, or would they? (I'm assuming they don't get > mapped using the rmap, so they are "different", and they are not managed by > lru). Right, neither type of page ends up on the LRU, and neither is added to rmap. > So I assume we only care about anon+file (lru-managed). Only these are > rmappable (besides hugetlb), correct? > > folio_test_lru_managed() > > Might be cleanest to describe anon+file that are managed by the lru, just > might not be on a lru list right now (difference to folio_test_lru()). Something I didn't think about last night is that this flag only _exists_ for large folios. folio_test_lru_managed() (and folio_test_rmappable()) both sound like they might work if you call them on single-page folios, but we BUG if you do (see folio_flags()) > I've been also thinking about > > "folio_test_normal" > > But it only makes sense when "all others (including hugetlb) are the odd > one". Who's to say slab is abnormal? ;-) But this one also fails to communicate "only call this on large folios". folio_test_splittable() does at least communicate that this is related to large folios, although one might simply expect it to return false for single-page folios rather than BUG. folio_test_large_rmappable()?
