Re: [PATCH v12 mm-new 04/15] khugepaged: generalize alloc_charge_folio()

[Lance Yang <lance.yang@linux.dev>]

On 2025/10/23 02:37, Nico Pache wrote:
> From: Dev Jain <dev.jain@arm.com>
> 
> Pass order to alloc_charge_folio() and update mTHP statistics.
> 
> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Acked-by: David Hildenbrand <david@redhat.com>
> Co-developed-by: Nico Pache <npache@redhat.com>
> Signed-off-by: Nico Pache <npache@redhat.com>
> Signed-off-by: Dev Jain <dev.jain@arm.com>
> ---

Cool! LGTM.

Reviewed-by: Lance Yang <lance.yang@linux.dev>

>   Documentation/admin-guide/mm/transhuge.rst |  8 ++++++++
>   include/linux/huge_mm.h                    |  2 ++
>   mm/huge_memory.c                           |  4 ++++
>   mm/khugepaged.c                            | 17 +++++++++++------
>   4 files changed, 25 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> index 1654211cc6cf..13269a0074d4 100644
> --- a/Documentation/admin-guide/mm/transhuge.rst
> +++ b/Documentation/admin-guide/mm/transhuge.rst
> @@ -634,6 +634,14 @@ anon_fault_fallback_charge
>   	instead falls back to using huge pages with lower orders or
>   	small pages even though the allocation was successful.
>   
> +collapse_alloc
> +	is incremented every time a huge page is successfully allocated for a
> +	khugepaged collapse.
> +
> +collapse_alloc_failed
> +	is incremented every time a huge page allocation fails during a
> +	khugepaged collapse.
> +
>   zswpout
>   	is incremented every time a huge page is swapped out to zswap in one
>   	piece without splitting.
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 7698b3542c4f..3d29624c4f3f 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -128,6 +128,8 @@ enum mthp_stat_item {
>   	MTHP_STAT_ANON_FAULT_ALLOC,
>   	MTHP_STAT_ANON_FAULT_FALLBACK,
>   	MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
> +	MTHP_STAT_COLLAPSE_ALLOC,
> +	MTHP_STAT_COLLAPSE_ALLOC_FAILED,
>   	MTHP_STAT_ZSWPOUT,
>   	MTHP_STAT_SWPIN,
>   	MTHP_STAT_SWPIN_FALLBACK,
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 370ecfd6a182..0063d1ba926e 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -620,6 +620,8 @@ static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
>   DEFINE_MTHP_STAT_ATTR(anon_fault_alloc, MTHP_STAT_ANON_FAULT_ALLOC);
>   DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK);
>   DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
> +DEFINE_MTHP_STAT_ATTR(collapse_alloc, MTHP_STAT_COLLAPSE_ALLOC);
> +DEFINE_MTHP_STAT_ATTR(collapse_alloc_failed, MTHP_STAT_COLLAPSE_ALLOC_FAILED);
>   DEFINE_MTHP_STAT_ATTR(zswpout, MTHP_STAT_ZSWPOUT);
>   DEFINE_MTHP_STAT_ATTR(swpin, MTHP_STAT_SWPIN);
>   DEFINE_MTHP_STAT_ATTR(swpin_fallback, MTHP_STAT_SWPIN_FALLBACK);
> @@ -685,6 +687,8 @@ static struct attribute *any_stats_attrs[] = {
>   #endif
>   	&split_attr.attr,
>   	&split_failed_attr.attr,
> +	&collapse_alloc_attr.attr,
> +	&collapse_alloc_failed_attr.attr,
>   	NULL,
>   };
>   
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 6cf8700823f9..36ee659acfbb 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1061,21 +1061,26 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
>   }
>   
>   static int alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
> -			      struct collapse_control *cc)
> +		struct collapse_control *cc, unsigned int order)
>   {
>   	gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() :
>   		     GFP_TRANSHUGE);
>   	int node = collapse_find_target_node(cc);
>   	struct folio *folio;
>   
> -	folio = __folio_alloc(gfp, HPAGE_PMD_ORDER, node, &cc->alloc_nmask);
> +	folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask);
>   	if (!folio) {
>   		*foliop = NULL;
> -		count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
> +		if (order == HPAGE_PMD_ORDER)
> +			count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
> +		count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC_FAILED);
>   		return SCAN_ALLOC_HUGE_PAGE_FAIL;
>   	}
>   
> -	count_vm_event(THP_COLLAPSE_ALLOC);
> +	if (order == HPAGE_PMD_ORDER)
> +		count_vm_event(THP_COLLAPSE_ALLOC);
> +	count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC);
> +
>   	if (unlikely(mem_cgroup_charge(folio, mm, gfp))) {
>   		folio_put(folio);
>   		*foliop = NULL;
> @@ -1112,7 +1117,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
>   	 */
>   	mmap_read_unlock(mm);
>   
> -	result = alloc_charge_folio(&folio, mm, cc);
> +	result = alloc_charge_folio(&folio, mm, cc, HPAGE_PMD_ORDER);
>   	if (result != SCAN_SUCCEED)
>   		goto out_nolock;
>   
> @@ -1850,7 +1855,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
>   	VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
>   	VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
>   
> -	result = alloc_charge_folio(&new_folio, mm, cc);
> +	result = alloc_charge_folio(&new_folio, mm, cc, HPAGE_PMD_ORDER);
>   	if (result != SCAN_SUCCEED)
>   		goto out;
>