Re: [PATCH v4 11/12] khugepaged: add per-order mTHP khugepaged stats

[Nico Pache <npache@redhat.com>]

On Thu, Apr 24, 2025 at 1:58 AM Baolin Wang
<baolin.wang@linux.alibaba.com> wrote:
>
>
>
> On 2025/4/17 08:02, Nico Pache wrote:
> > With mTHP support inplace, let add the per-order mTHP stats for
> > exceeding NONE, SWAP, and SHARED.
> >
> > Signed-off-by: Nico Pache <npache@redhat.com>
> > ---
> >   include/linux/huge_mm.h |  3 +++
> >   mm/huge_memory.c        |  7 +++++++
> >   mm/khugepaged.c         | 16 +++++++++++++---
> >   3 files changed, 23 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index 55b242335420..782d3a7854b4 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -139,6 +139,9 @@ enum mthp_stat_item {
> >       MTHP_STAT_SPLIT_DEFERRED,
> >       MTHP_STAT_NR_ANON,
> >       MTHP_STAT_NR_ANON_PARTIALLY_MAPPED,
> > +     MTHP_STAT_COLLAPSE_EXCEED_SWAP,
> > +     MTHP_STAT_COLLAPSE_EXCEED_NONE,
> > +     MTHP_STAT_COLLAPSE_EXCEED_SHARED,
> >       __MTHP_STAT_COUNT
> >   };
> >
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 7798c9284533..de4704af0022 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -633,6 +633,10 @@ DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED);
> >   DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED);
> >   DEFINE_MTHP_STAT_ATTR(nr_anon, MTHP_STAT_NR_ANON);
> >   DEFINE_MTHP_STAT_ATTR(nr_anon_partially_mapped, MTHP_STAT_NR_ANON_PARTIALLY_MAPPED);
> > +DEFINE_MTHP_STAT_ATTR(collapse_exceed_swap_pte, MTHP_STAT_COLLAPSE_EXCEED_SWAP);
> > +DEFINE_MTHP_STAT_ATTR(collapse_exceed_none_pte, MTHP_STAT_COLLAPSE_EXCEED_NONE);
> > +DEFINE_MTHP_STAT_ATTR(collapse_exceed_shared_pte, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
> > +
> >
> >   static struct attribute *anon_stats_attrs[] = {
> >       &anon_fault_alloc_attr.attr,
> > @@ -649,6 +653,9 @@ static struct attribute *anon_stats_attrs[] = {
> >       &split_deferred_attr.attr,
> >       &nr_anon_attr.attr,
> >       &nr_anon_partially_mapped_attr.attr,
> > +     &collapse_exceed_swap_pte_attr.attr,
> > +     &collapse_exceed_none_pte_attr.attr,
> > +     &collapse_exceed_shared_pte_attr.attr,
> >       NULL,
> >   };
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 67da0950b833..38643a681ba5 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -604,7 +604,10 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> >                               continue;
> >                       } else {
> >                               result = SCAN_EXCEED_NONE_PTE;
> > -                             count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
> > +                             if (order == HPAGE_PMD_ORDER)
> > +                                     count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
> > +                             else
> > +                                     count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_NONE);
> >                               goto out;
> >                       }
> >               }
> > @@ -633,8 +636,14 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> >               /* See khugepaged_scan_pmd(). */
> >               if (folio_maybe_mapped_shared(folio)) {
> >                       ++shared;
> > -                     if (order != HPAGE_PMD_ORDER || (cc->is_khugepaged &&
> > -                         shared > khugepaged_max_ptes_shared)) {
> > +                     if (order != HPAGE_PMD_ORDER) {
> > +                             result = SCAN_EXCEED_SHARED_PTE;
> > +                             count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
> > +                             goto out;
> > +                     }
> > +
> > +                     if (cc->is_khugepaged &&
> > +                             shared > khugepaged_max_ptes_shared) {
> >                               result = SCAN_EXCEED_SHARED_PTE;
> >                               count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
> >                               goto out;
> > @@ -1060,6 +1069,7 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
> >
> >               /* Dont swapin for mTHP collapse */
> >               if (order != HPAGE_PMD_ORDER) {
> > +                     count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
>
> Should be MTHP_STAT_COLLAPSE_EXCEED_SWAP?
Yes! Thank you, I will fix this :)
>
> >                       result = SCAN_EXCEED_SWAP_PTE;
> >                       goto out;
> >               }
>