Re: [PATCH 9/8] mm: Account PMD tables like PTE tables

[Mike Rapoport]

On Sat, Jun 27, 2020 at 07:46:42PM +0100, Matthew Wilcox wrote:
> We account the PTE level of the page tables to the process in order to
> make smarter OOM decisions and help diagnose why memory is fragmented.
> For these same reasons, we should account pages allocated for PMDs.
> With larger process address spaces and ASLR, the number of PMDs in use
> is higher than it used to be so the inaccuracy is starting to matter.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>

Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>

> ---
>  include/linux/mm.h | 24 ++++++++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index dc7b87310c10..b283e25fcffa 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2271,7 +2271,7 @@ static inline spinlock_t *pmd_lockptr(struct mm_struct *mm, pmd_t *pmd)
>  	return ptlock_ptr(pmd_to_page(pmd));
>  }
>  
> -static inline bool pgtable_pmd_page_ctor(struct page *page)
> +static inline bool pmd_ptlock_init(struct page *page)
>  {
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  	page->pmd_huge_pte = NULL;
> @@ -2279,7 +2279,7 @@ static inline bool pgtable_pmd_page_ctor(struct page *page)
>  	return ptlock_init(page);
>  }
>  
> -static inline void pgtable_pmd_page_dtor(struct page *page)
> +static inline void pmd_ptlock_free(struct page *page)
>  {
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  	VM_BUG_ON_PAGE(page->pmd_huge_pte, page);
> @@ -2296,8 +2296,8 @@ static inline spinlock_t *pmd_lockptr(struct mm_struct *mm, pmd_t *pmd)
>  	return &mm->page_table_lock;
>  }
>  
> -static inline bool pgtable_pmd_page_ctor(struct page *page) { return true; }
> -static inline void pgtable_pmd_page_dtor(struct page *page) {}
> +static inline bool pmd_ptlock_init(struct page *page) { return true; }
> +static inline void pmd_ptlock_free(struct page *page) {}
>  
>  #define pmd_huge_pte(mm, pmd) ((mm)->pmd_huge_pte)
>  
> @@ -2310,6 +2310,22 @@ static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd)
>  	return ptl;
>  }
>  
> +static inline bool pgtable_pmd_page_ctor(struct page *page)
> +{
> +	if (!pmd_ptlock_init(page))
> +		return false;
> +	__SetPageTable(page);
> +	inc_zone_page_state(page, NR_PAGETABLE);
> +	return true;
> +}
> +
> +static inline void pgtable_pmd_page_dtor(struct page *page)
> +{
> +	pmd_ptlock_free(page);
> +	__ClearPageTable(page);
> +	dec_zone_page_state(page, NR_PAGETABLE);
> +}
> +
>  /*
>   * No scalability reason to split PUD locks yet, but follow the same pattern
>   * as the PMD locks to make it easier if we decide to.  The VM should not be
> -- 
> 2.27.0
> 

-- 
Sincerely yours,
Mike.