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

[Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>]

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@xxxxxxxxxx>
> ---
>   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?

>   			result = SCAN_EXCEED_SWAP_PTE;
>   			goto out;
>   		}