On Thu, Apr 25, 2024 at 5:01 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 25.04.24 10:50, Lance Yang wrote: > > Hey Zi, David, > > Hi, > > > > > How about this change(diff against mm-unstable) as follows? > > goes into the right direction, please resent the whole thing, that will > make it easier to review. Got it. I‘ll keep that in mind, thanks! > > > > > I'd like to add __try_to_unmap_huge_pmd() as a new internal function > > specifically for unmapping PMD-mapped folios. If, for any reason, we cannot > > unmap the folio, then we'll still split it as previously done. > > > > Currently, __try_to_unmap_huge_pmd() only handles lazyfree THPs, but it > > can be extended to support other large folios that are PMD-mapped in the > > future if needed. > > > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > > index 670218f762c8..0f906dc6d280 100644 > > --- a/include/linux/rmap.h > > +++ b/include/linux/rmap.h > > @@ -100,8 +100,6 @@ enum ttu_flags { > > * do a final flush if necessary */ > > TTU_RMAP_LOCKED = 0x80, /* do not grab rmap lock: > > * caller holds it */ > > - TTU_LAZYFREE_THP = 0x100, /* avoid splitting PMD-mapped THPs > > - * that are marked as lazyfree. */ > > }; > > > > #ifdef CONFIG_MMU > > diff --git a/mm/rmap.c b/mm/rmap.c > > index a7913a454028..879c8923abfc 100644 > > --- a/mm/rmap.c > > +++ b/mm/rmap.c > > @@ -1606,6 +1606,19 @@ void folio_remove_rmap_pmd(struct folio *folio, struct page *page, > > #endif > > } > > > > +static bool __try_to_unmap_huge_pmd(struct vm_area_struct *vma, > > + unsigned long addr, struct folio *folio) > > +{ > > + VM_WARN_ON_FOLIO(!folio_test_pmd_mappable(folio), folio); > > + > > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > > + if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) > > + return discard_trans_pmd(vma, addr, folio); > > +#endif > > + > > + return false; > > +} > > + > > /* > > * @arg: enum ttu_flags will be passed to this argument > > */ > > @@ -1631,14 +1644,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > > if (flags & TTU_SYNC) > > pvmw.flags = PVMW_SYNC; > > > > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > > - if (flags & TTU_LAZYFREE_THP) > > - if (discard_trans_pmd(vma, address, folio)) > > + if (flags & TTU_SPLIT_HUGE_PMD) { > > + if (__try_to_unmap_huge_pmd(vma, address, folio)) > > return true; > > -#endif > > - > > - if (flags & TTU_SPLIT_HUGE_PMD) > > split_huge_pmd_address(vma, address, false, folio); > > + } > > > > I was wondering if we can better integrate that into the pagewalk below. > > That is, don't do the TTU_SPLIT_HUGE_PMD immediately. Start the pagewalk > first. If we walk a PMD, try to unmap it. Only if that fails, split it. Nice. Thanks for the suggestion! I'll work on integrating it into the pagewalk as you suggested. > > Less working on "vma + address" and instead directly on PMDs. Yes, some of the work on "vma + address" can be avoided :) Thanks again for the review! Lance > > -- > Cheers, > > David / dhildenb >