Re: [PATCH v9 10/14] khugepaged: allow khugepaged to check all anonymous mTHP orders

[Nico Pache]

On Wed, Jul 16, 2025 at 9:28 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> On 14.07.25 02:32, Nico Pache wrote:
> > From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
>
> Should the subject better be
>
> "mm/khugepaged: enable collapsing mTHPs even when PMD THPs are disabled"
Thank does read better.
>
> (in general, I assume all subjects should be prefixed by "mm/khugepaged:")
ehhh, seems like there's a mix of "mm/khugepaged", "khugepaged", and
"mm: khugepaged:" being used in other commits. I prefer using
khugepaged as it leaves me more space for the commit title
>
> >
> > We have now allowed mTHP collapse, but thp_vma_allowable_order() still only
> > checks if the PMD-sized mTHP is allowed to collapse. This prevents scanning
> > and collapsing of 64K mTHP when only 64K mTHP is enabled. Thus, we should
> > modify the checks to allow all large orders of anonymous mTHP.
> >
> > Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Nico Pache <npache@xxxxxxxxxx>
> > ---
> >   mm/khugepaged.c | 13 +++++++++----
> >   1 file changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 7a9c4edf0e23..3772dc0d78ea 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -491,8 +491,11 @@ void khugepaged_enter_vma(struct vm_area_struct *vma,
> >   {
> >       if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
> >           hugepage_pmd_enabled()) {
> > -             if (thp_vma_allowable_order(vma, vm_flags, TVA_ENFORCE_SYSFS,
> > -                                         PMD_ORDER))
> > +             unsigned long orders = vma_is_anonymous(vma) ?
> > +                                     THP_ORDERS_ALL_ANON : BIT(PMD_ORDER);
> > +
> > +             if (thp_vma_allowable_orders(vma, vm_flags, TVA_ENFORCE_SYSFS,
> > +                                         orders))
> >                       __khugepaged_enter(vma->vm_mm);
> >       }
> >   }
> > @@ -2624,6 +2627,8 @@ static unsigned int collapse_scan_mm_slot(unsigned int pages, int *result,
> >
> >       vma_iter_init(&vmi, mm, khugepaged_scan.address);
> >       for_each_vma(vmi, vma) {
> > +             unsigned long orders = vma_is_anonymous(vma) ?
> > +                                     THP_ORDERS_ALL_ANON : BIT(PMD_ORDER);
> >               unsigned long hstart, hend;
> >
> >               cond_resched();
> > @@ -2631,8 +2636,8 @@ static unsigned int collapse_scan_mm_slot(unsigned int pages, int *result,
> >                       progress++;
> >                       break;
> >               }
> > -             if (!thp_vma_allowable_order(vma, vma->vm_flags,
> > -                                     TVA_ENFORCE_SYSFS, PMD_ORDER)) {
> > +             if (!thp_vma_allowable_orders(vma, vma->vm_flags,
> > +                     TVA_ENFORCE_SYSFS, orders)) {
> >   skip:
> >                       progress++;
> >                       continue;
>
> Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Thank you for your review :)

>
> --
> Cheers,
>
> David / dhildenb
>