Re: [PATCH v10 12/13] khugepaged: add per-order mTHP khugepaged stats

[Nico Pache <npache@redhat.com>]

On Tue, Aug 19, 2025 at 7:49 AM Nico Pache <npache@redhat.com> 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>

I had git send email error and had to resend this patch (12) and patch
13, but i forgot the in-reply-to
please ignore this one and reply to correct version

https://lore.kernel.org/lkml/20250819141610.626140-1-npache@redhat.com/
--in-reply-to=20250819141610.626140-1-npache@redhat.com


-- Nico

> ---
>  Documentation/admin-guide/mm/transhuge.rst | 17 +++++++++++++++++
>  include/linux/huge_mm.h                    |  3 +++
>  mm/huge_memory.c                           |  7 +++++++
>  mm/khugepaged.c                            | 16 +++++++++++++---
>  4 files changed, 40 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> index 7ccb93e22852..b85547ac4fe9 100644
> --- a/Documentation/admin-guide/mm/transhuge.rst
> +++ b/Documentation/admin-guide/mm/transhuge.rst
> @@ -705,6 +705,23 @@ nr_anon_partially_mapped
>         an anonymous THP as "partially mapped" and count it here, even though it
>         is not actually partially mapped anymore.
>
> +collapse_exceed_swap_pte
> +       The number of anonymous THP which contain at least one swap PTE.
> +       Currently khugepaged does not support collapsing mTHP regions that
> +       contain a swap PTE.
> +
> +collapse_exceed_none_pte
> +       The number of anonymous THP which have exceeded the none PTE threshold.
> +       With mTHP collapse, a bitmap is used to gather the state of a PMD region
> +       and is then recursively checked from largest to smallest order against
> +       the scaled max_ptes_none count. This counter indicates that the next
> +       enabled order will be checked.
> +
> +collapse_exceed_shared_pte
> +       The number of anonymous THP which contain at least one shared PTE.
> +       Currently khugepaged does not support collapsing mTHP regions that
> +       contain a shared PTE.
> +
>  As the system ages, allocating huge pages may be expensive as the
>  system uses memory compaction to copy data around memory to free a
>  huge page for use. There are some counters in ``/proc/vmstat`` to help
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 4ada5d1f7297..6f1593d0b4b5 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -144,6 +144,9 @@ 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 20d005c2c61f..9f0470c3e983 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -639,6 +639,10 @@ 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,
> @@ -655,6 +659,9 @@ 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 c13bc583a368..5a3386043f39 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -594,7 +594,9 @@ 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);
> +                               count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_NONE);
>                                 goto out;
>                         }
>                 }
> @@ -633,10 +635,17 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>                          * shared may cause a future higher order collapse on a
>                          * rescan of the same range.
>                          */
> -                       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);
> +                               count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
>                                 goto out;
>                         }
>                 }
> @@ -1084,6 +1093,7 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
>                  * range.
>                  */
>                 if (order != HPAGE_PMD_ORDER) {
> +                       count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SWAP);
>                         pte_unmap(pte);
>                         mmap_read_unlock(mm);
>                         result = SCAN_EXCEED_SWAP_PTE;
> --
> 2.50.1
>