Re: [RFC PATCH 1/8] arm64/hugetlb: Extend batching of multiple CONT_PTE in a single PTE setup

[Barry Song <baohua@kernel.org>]

On Wed, Apr 8, 2026 at 6:32 PM Dev Jain <dev.jain@arm.com> wrote:
>
>
>
> On 08/04/26 8:21 am, Barry Song (Xiaomi) wrote:
> > For sizes aligned to CONT_PTE_SIZE and smaller than PMD_SIZE,
> > we can batch CONT_PTE settings instead of handling them individually.
> >
> > Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
> > ---
> >  arch/arm64/mm/hugetlbpage.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> > index a42c05cf5640..bf31c11ebd3b 100644
> > --- a/arch/arm64/mm/hugetlbpage.c
> > +++ b/arch/arm64/mm/hugetlbpage.c
> > @@ -110,6 +110,12 @@ static inline int num_contig_ptes(unsigned long size, size_t *pgsize)
> >               contig_ptes = CONT_PTES;
> >               break;
> >       default:
> > +             if (size < CONT_PMD_SIZE && size > 0 &&
> > +                             IS_ALIGNED(size, CONT_PTE_SIZE)) {
>
> Nit: Having the lower bound check before upper bound is natural to
> read, so this should be size > 0 && size < CONT_PMD_SIZE (i.e written
> the other way around).

Thanks very much for reviewing, Dev. As we discussed in patch 0/8,
this should be
PMD_SIZE, not CONT_PMD_SIZE. I will use size > 0 && size < PMD_SIZE
in the next version.

>
> Also IS_ALIGNED needs to go below size.

Sure, thanks!

>
>
> > +                     contig_ptes = size >> PAGE_SHIFT;
> > +                     *pgsize = PAGE_SIZE;
> > +                     break;
> > +             }
> >               WARN_ON(!__hugetlb_valid_size(size));
> >       }
> >
> > @@ -359,6 +365,10 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
> >       case CONT_PTE_SIZE:
> >               return pte_mkcont(entry);
> >       default:
> > +             if (pagesize < CONT_PMD_SIZE && pagesize > 0 &&
> > +                             IS_ALIGNED(pagesize, CONT_PTE_SIZE))
> > +                     return pte_mkcont(entry);

Here it should be pagesize > 0 && pagesize < PMD_SIZE as well :-)

> > +
> >               break;
> >       }
> >       pr_warn("%s: unrecognized huge page size 0x%lx\n",
>

Best Regards
Barry