On Thu, 15 Aug 2024 16:31:01 +0800 Huan Yang <link@xxxxxxxx> wrote: > Current try_to_map_unused_to_zeropage try to use shared zero page to > save some memory of sub page. > > If forbids zeropage, no need to do anything rather than attempting to > assess wthether to use it afterwards. > > ... > > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -192,6 +192,9 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, > VM_BUG_ON_PAGE(!PageLocked(page), page); > VM_BUG_ON_PAGE(pte_present(*pvmw->pte), page); > > + if (mm_forbids_zeropage(pvmw->vma->vm_mm)) > + return false; > + > if (PageMlocked(page) || (pvmw->vma->vm_flags & VM_LOCKED)) > return false; > > @@ -204,7 +207,7 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, > contains_data = memchr_inv(addr, 0, PAGE_SIZE); > kunmap_local(addr); > > - if (contains_data || mm_forbids_zeropage(pvmw->vma->vm_mm)) > + if (contains_data) > return false; > Looks sensible. I'll add it as a fixup to "mm: remap unused subpages to shared zeropage when splitting isolated thp".
