Re: [PATCH 1/1] mm/mlock: implement folio_mlock_step() using folio_pte_batch()

[David Hildenbrand]

On 03.06.24 10:58, Baolin Wang wrote:
> On 2024/6/3 12:14, Barry Song wrote:
> > On Mon, Jun 3, 2024 at 3:31 PM Lance Yang <ioworker0@xxxxxxxxx> wrote:
> > > Let's make folio_mlock_step() simply a wrapper around folio_pte_batch(),
> > > which will greatly reduce the cost of ptep_get() when scanning a range of
> > > contptes.
> > >
> > > Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
> > > ---
> > >    mm/mlock.c | 23 ++++++-----------------
> > >    1 file changed, 6 insertions(+), 17 deletions(-)
> > >
> > > diff --git a/mm/mlock.c b/mm/mlock.c
> > > index 30b51cdea89d..1ae6232d38cf 100644
> > > --- a/mm/mlock.c
> > > +++ b/mm/mlock.c
> > > @@ -307,26 +307,15 @@ void munlock_folio(struct folio *folio)
> > >    static inline unsigned int folio_mlock_step(struct folio *folio,
> > >                   pte_t *pte, unsigned long addr, unsigned long end)
> > >    {
> > > -       unsigned int count, i, nr = folio_nr_pages(folio);
> > > -       unsigned long pfn = folio_pfn(folio);
> > > -       pte_t ptent = ptep_get(pte);
> > > -
> > > -       if (!folio_test_large(folio))
> > > +       if (likely(!folio_test_large(folio)))
> > >                   return 1;
> > >
> > > -       count = pfn + nr - pte_pfn(ptent);
> > > -       count = min_t(unsigned int, count, (end - addr) >> PAGE_SHIFT);
> > > -
> > > -       for (i = 0; i < count; i++, pte++) {
> > > -               pte_t entry = ptep_get(pte);
> > > -
> > > -               if (!pte_present(entry))
> > > -                       break;
> > > -               if (pte_pfn(entry) - pfn >= nr)
> > > -                       break;
> > > -       }
> > > +       const fpb_t fpb_flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY;
> > > +       int max_nr = (end - addr) / PAGE_SIZE;
> > > +       pte_t ptent = ptep_get(pte);
> > >
> > > -       return i;
> > > +       return folio_pte_batch(folio, addr, pte, ptent, max_nr, fpb_flags, NULL,
> > > +                              NULL, NULL);
> > >    }
> >
> > what about a minimum change as below?
> > index 30b51cdea89d..e8b98f84fbd2 100644
> > --- a/mm/mlock.c
> > +++ b/mm/mlock.c
> > @@ -307,26 +307,15 @@ void munlock_folio(struct folio *folio)
> >    static inline unsigned int folio_mlock_step(struct folio *folio,
> >                   pte_t *pte, unsigned long addr, unsigned long end)
> >    {
> > -       unsigned int count, i, nr = folio_nr_pages(folio);
> > -       unsigned long pfn = folio_pfn(folio);
> > +       unsigned int count = (end - addr) >> PAGE_SHIFT;
> >           pte_t ptent = ptep_get(pte);
> > +       const fpb_t fpb_flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY;
> >
> >           if (!folio_test_large(folio))
> >                   return 1;
> >
> > -       count = pfn + nr - pte_pfn(ptent);
> > -       count = min_t(unsigned int, count, (end - addr) >> PAGE_SHIFT);
> > -
> > -       for (i = 0; i < count; i++, pte++) {
> > -               pte_t entry = ptep_get(pte);
> > -
> > -               if (!pte_present(entry))
> > -                       break;
> > -               if (pte_pfn(entry) - pfn >= nr)
> > -                       break;
> > -       }
> > -
> > -       return i;
> > +       return folio_pte_batch(folio, addr, pte, ptent, count, fpb_flags, NULL,
> > +                              NULL, NULL);
> >    }
>
> LGTM.
> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb