Hey Ryan, David,
Thanks for taking time to review!
On Wed, Apr 17, 2024 at 12:52 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> >> + nr = madvise_folio_pte_batch(addr, end, folio, pte,
> >> + ptent, &any_young, &any_dirty);
> >> +
> >> + if (nr < folio_nr_pages(folio)) {
> >> + if (folio_likely_mapped_shared(folio))
> >> + continue;
> >> +
> >> + arch_leave_lazy_mmu_mode();
> >> + if (madvise_pte_split_folio(mm, pmd, addr,
> >> + folio, &start_pte, &ptl))
> >> + nr = 0;
> >> + if (!start_pte)
> >> + break;
> >> + pte = start_pte;
> >> + arch_enter_lazy_mmu_mode();
> >> + continue;
> >> + }
> >> +
> >> + if (any_young)
> >> + ptent = pte_mkyoung(ptent);
> >> + if (any_dirty)
> >> + ptent = pte_mkdirty(ptent);
> >> }
> >>
> >> + if (folio_mapcount(folio) != folio_nr_pages(folio))
> >> + continue;
> >
> > Why is this here? I thought we had previously concluded to only do this test
> > inside the below if statement (where you have it duplicated).
My bad for this mistake - sorry!
>
> I stumbled over these same while reviewing. It's not exactly duplicate,
> because it's unreliable without the folio lock. It looks more like an
> best-effort early check.
>
> But then, we also add it to cases where we previously wouldn't check the
> mapcount at all: when the folio was added to the swapcache or is already
> dirty.
>
> In that case, we would even see a change for order-0 folios with that
> new check.
Thanks for pointing that out! I'll remove this check here in the next version.
I overlooked that this is a new check for order-0 folios :(
Thanks,
Lance
>
> --
> Cheers,
>
> David / dhildenb
>
