On Thu, May 22, 2025 at 02:50:20PM +0200, David Hildenbrand wrote: > On 22.05.25 14:34, Pankaj Raghav (Samsung) wrote: > > Hi David, > > > > > > config ARCH_WANTS_THP_SWAP > > > > def_bool n > > > > -config ARCH_WANTS_THP_ZERO_PAGE_ALWAYS > > > > +config ARCH_WANTS_HUGE_ZERO_PAGE_ALWAYS > > > > def_bool n > > > > +config HUGE_ZERO_PAGE_ALWAYS > > > > > > Likely something like > > > > > > PMD_ZERO_PAGE > > > > > > Will be a lot clearer. > > > > Sounds much better :) > > And maybe something like > > "STATIC_PMD_ZERO_PAGE" > > would be even clearer. > > The other one would be the dynamic one. Got it. So if I understand correctly, we are going to have two huge zero pages, - one that is always allocated statically. - the existing dynamic will still be there for the existing users. > > > > > > > > > > + def_bool y> + depends on HUGETLB_PAGE && > > > ARCH_WANTS_HUGE_ZERO_PAGE_ALWAYS > > > > > > I suspect it should then also be independent of HUGETLB_PAGE? > > > > You are right. So we don't depend on any of these features. > > > > > > > > > + help > > > > + Typically huge_zero_folio, which is a huge page of zeroes, is allocated > > > > + on demand and deallocated when not in use. This option will always > > > > + allocate huge_zero_folio for zeroing and it is never deallocated. > > > > + Not suitable for memory constrained systems. > > > > > > I assume that code then has to live in mm/memory.c ? > > > > Hmm, then huge_zero_folio should have always been in mm/memory.c to > > begin with? > > > > It's complicated. Only do_huge_pmd_anonymous_page() (and fsdax) really uses > it, and it may only get mapped into a process under certain conditions > (related to THP / PMD handling). > Got it. > > > > So IIUC your comment, we should move the huge_zero_page_init() in the > > first patch to mm/memory.c and the existing shrinker code can be a part > > where they already are? > > Good question. At least the "static" part can easily be moved over. Maybe > the dynamic part as well. > > Worth trying it out and seeing how it looks :) Challenge accepted ;) Thanks for the comments David. -- Pankaj
