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

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Date:   Sun, 28 Jun 2020 09:59:51 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org,
        Abdul Haleem <abdhalee@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Joerg Roedel <joro@...tes.org>,
        Max Filippov <jcmvbkbc@...il.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Satheesh Rajendran <sathnaga@...ux.vnet.ibm.com>,
        Stafford Horne <shorne@...il.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-alpha@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        linux-mm@...ck.org, linux-parisc@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-um@...ts.infradead.org, linux-xtensa@...ux-xtensa.org,
        linuxppc-dev@...ts.ozlabs.org, openrisc@...ts.librecores.org,
        sparclinux@...r.kernel.org
Subject: Re: [PATCH 9/8] mm: Account PMD tables like PTE tables

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@...radead.org>

Reviewed-by: Mike Rapoport <rppt@...ux.ibm.com>

> ---
>  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.