On Tue, Aug 15, 2023 at 06:40:55PM +0200, David Hildenbrand wrote: > On 15.08.23 17:32, Matthew Wilcox wrote: > > On Tue, Aug 15, 2023 at 09:54:36AM +0200, David Hildenbrand wrote: > > > On 15.08.23 05:26, Matthew Wilcox (Oracle) wrote: > > > > Stored in the first tail page's flags, this flag replaces the destructor. > > > > That removes the last of the destructors, so remove all references to > > > > folio_dtor and compound_dtor. > > > > > > > > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > > > > --- > > > > > > [...] > > > > > > > + /* Has a deferred list (may be empty). First tail page. */ > > > > + PG_deferred_list = PG_reclaim, > > > > + > > > > > > If PG_deferred_list implies thp (and replaces the thp dtor), should we > > > rather name this PG_thp or something along those lines? > > > > We're trying to use 'thp' to mean 'a folio which is pmd mappable', > > so I'd rather not call it that. > > There is no conclusion on that. Theree are a lot of counters called THP and TransHuge and other variants which are exposed to userspace, and the (user) assumption is that this counts PMD-sized folios. If you grep around for folio_test_pmd_mappable(), you'll find them. If we have folio_test_thp(), people will write: if (folio_test_thp(folio)) __mod_lruvec_state(lruvec, NR_SHMEM_THPS, nr); instead of using folio_test_pmd_mappable(). > After all, the deferred split queue is just an implementation detail, and it > happens to live in tailpage 2, no? > > Once we would end up initializing something else in prep_transhuge_page(), > it would turn out pretty confusing if that is called folio_remove_deferred() > ... Perhaps the key difference between normal compound pages and file/anon compound pages is that the latter are splittable? So we can name all of this: folio_init_splittable() folio_test_splittable() folio_fini_splittable() Maybe that's still too close to an implementation detail, but it's at least talking about _a_ characteristic of the folio, even if it's not the _only_ characteristic of the folio.
