On Mon, Jan 6, 2025 at 5:34 PM Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> wrote: > > > > On 2025/1/6 17:03, Barry Song wrote: > > On Mon, Jan 6, 2025 at 7:40 PM Baolin Wang > > <baolin.wang@xxxxxxxxxxxxxxxxx> wrote: > >> > >> > >> > >> On 2025/1/6 11:17, Barry Song wrote: > >>> From: Barry Song <v-songbaohua@xxxxxxxx> > >>> > >>> The refcount may be temporarily or long-term increased, but this does > >>> not change the fundamental nature of the folio already being lazy- > >>> freed. Therefore, we only reset 'swapbacked' when we are certain the > >>> folio is dirty and not droppable. > >>> > >>> Suggested-by: David Hildenbrand <david@xxxxxxxxxx> > >>> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> > >> > >> The changes look good to me. While we are at it, could you also change > >> the __discard_anon_folio_pmd_locked() to follow the same strategy for > >> lazy-freed PMD-sized folio? > > > > it seems you mean __discard_anon_folio_pmd_locked() is lacking > > folio_set_swapbacked(folio) for dirty pmd-mapped folios? Good catch! Hmm... I don't recall why we don't call folio_set_swapbacked for dirty THPs in __discard_anon_folio_pmd_locked() - possibly to align with previous behavior ;) If a dirty PMD-mapped THP cannot be discarded, we just split it and restart the page walk to process the PTE-mapped THP. After that, we will only mark each folio within the THP as swap-backed individually. It seems like we could cut the work by calling folio_set_swapbacked() for dirty THPs directly in __discard_anon_folio_pmd_locked(), skipping the restart of the page walk after splitting the THP, IMHO ;) Thanks, Lance > > and it seems !(vma->vm_flags & VM_DROPPABLE) is also not > > handled properly? > > Right.
