linux-kernel - Re: [RFC PATCH v3 1/3] mm: Factor out the pagetable pages account into new helper function

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Date:   Thu, 30 Jun 2022 17:11:33 +0300
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, willy@...radead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3 1/3] mm: Factor out the pagetable pages account
 into new helper function

On Thu, Jun 30, 2022 at 07:11:14PM +0800, Baolin Wang wrote:
> Factor out the pagetable pages account into new helper functions to avoid
> duplicated code. Meanwhile these helper functions also will be used to
> account pagetable pages which do not need split pagetale lock.
> 
> Meanwhile convert to use mod_lruvec_page_state() in case of non-order-0
> page table allocation.

These are *very* rare. I think only parisc may have non-order-0 pmd and pud
tables.
With that, I'd suggest making use of compound_nr() build time opt-in.
 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---
>  include/linux/mm.h | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index a2270e3..3be6d2c 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2353,20 +2353,30 @@ static inline void pgtable_init(void)
>  	pgtable_cache_init();
>  }
>  
> +static inline void pgtable_page_inc(struct page *page)
> +{
> +	__SetPageTable(page);
> +	mod_lruvec_page_state(page, NR_PAGETABLE, compound_nr(page));
> +}
> +
> +static inline void pgtable_page_dec(struct page *page)
> +{
> +	__ClearPageTable(page);
> +	mod_lruvec_page_state(page, NR_PAGETABLE, -compound_nr(page));
> +}
> +
>  static inline bool pgtable_pte_page_ctor(struct page *page)
>  {
>  	if (!ptlock_init(page))
>  		return false;
> -	__SetPageTable(page);
> -	inc_lruvec_page_state(page, NR_PAGETABLE);
> +	pgtable_page_inc(page);
>  	return true;
>  }
>  
>  static inline void pgtable_pte_page_dtor(struct page *page)
>  {
>  	ptlock_free(page);
> -	__ClearPageTable(page);
> -	dec_lruvec_page_state(page, NR_PAGETABLE);
> +	pgtable_page_dec(page);
>  }
>  
>  #define pte_offset_map_lock(mm, pmd, address, ptlp)	\
> @@ -2452,16 +2462,14 @@ static inline bool pgtable_pmd_page_ctor(struct page *page)
>  {
>  	if (!pmd_ptlock_init(page))
>  		return false;
> -	__SetPageTable(page);
> -	inc_lruvec_page_state(page, NR_PAGETABLE);
> +	pgtable_page_inc(page);
>  	return true;
>  }
>  
>  static inline void pgtable_pmd_page_dtor(struct page *page)
>  {
>  	pmd_ptlock_free(page);
> -	__ClearPageTable(page);
> -	dec_lruvec_page_state(page, NR_PAGETABLE);
> +	pgtable_page_dec(page);
>  }
>  
>  /*
> -- 
> 1.8.3.1
> 

-- 
Sincerely yours,
Mike.