linux-kernel - Re: [RFC PATCH v2 3/3] mm: Add kernel PTE level pagetable pages account

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Date:   Wed, 22 Jun 2022 09:44:29 -0500
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 v2 3/3] mm: Add kernel PTE level pagetable pages
 account

On Wed, Jun 22, 2022 at 04:58:54PM +0800, Baolin Wang wrote:
> Now the kernel PTE level ptes are always protected by mm->page_table_lock
> instead of split pagetable lock, so the kernel PTE level pagetable pages
> are not accounted. Especially the vmalloc()/vmap() can consume lots of
> kernel pagetable, so to get an accurate pagetable accounting, calling new
> helpers pgtable_set_and_inc()/pgtable_clear_and_dec() when allocating or
> freeing a kernel PTE level pagetable page.

This patch only adds accounting to the page tables allocated after boot,
please mention this in the changelog.
 
> Meanwhile converting architectures to use corresponding generic PTE pagetable
> allocation and freeing functions.
> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Reported-by: kernel test robot <oliver.sang@...el.com>
> ---
>  arch/csky/include/asm/pgalloc.h |  2 +-
>  arch/microblaze/mm/pgtable.c    |  2 +-
>  arch/openrisc/mm/ioremap.c      |  2 +-
>  arch/x86/mm/pgtable.c           |  5 ++++-
>  include/asm-generic/pgalloc.h   | 14 ++++++++++++--
>  5 files changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/csky/include/asm/pgalloc.h b/arch/csky/include/asm/pgalloc.h
> index bbbd069..2443226 100644
> --- a/arch/csky/include/asm/pgalloc.h
> +++ b/arch/csky/include/asm/pgalloc.h
> @@ -29,7 +29,7 @@ static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
>  	pte_t *pte;
>  	unsigned long i;
>  
> -	pte = (pte_t *) __get_free_page(GFP_KERNEL);
> +	pte = __pte_alloc_one_kernel(mm);
>  	if (!pte)
>  		return NULL;
>  
> diff --git a/arch/microblaze/mm/pgtable.c b/arch/microblaze/mm/pgtable.c
> index 9f73265..e96dd1b 100644
> --- a/arch/microblaze/mm/pgtable.c
> +++ b/arch/microblaze/mm/pgtable.c
> @@ -245,7 +245,7 @@ unsigned long iopa(unsigned long addr)
>  __ref pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
>  {
>  	if (mem_init_done)
> -		return (pte_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
> +		return __pte_alloc_one_kernel(mm);
>  	else
>  		return memblock_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
>  					      MEMBLOCK_LOW_LIMIT,
> diff --git a/arch/openrisc/mm/ioremap.c b/arch/openrisc/mm/ioremap.c
> index daae13a..3453acc 100644
> --- a/arch/openrisc/mm/ioremap.c
> +++ b/arch/openrisc/mm/ioremap.c
> @@ -118,7 +118,7 @@ pte_t __ref *pte_alloc_one_kernel(struct mm_struct *mm)
>  	pte_t *pte;
>  
>  	if (likely(mem_init_done)) {
> -		pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
> +		pte = __pte_alloc_one_kernel(mm);
>  	} else {
>  		pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
>  		if (!pte)
> diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> index a8ab3f9..fc2b9ef 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -851,6 +851,7 @@ int pud_free_pmd_page(pud_t *pud, unsigned long addr)
>  int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
>  {
>  	pte_t *pte;
> +	struct page *page;
>  
>  	pte = (pte_t *)pmd_page_vaddr(*pmd);
>  	pmd_clear(pmd);
> @@ -858,7 +859,9 @@ int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
>  	/* INVLPG to clear all paging-structure caches */
>  	flush_tlb_kernel_range(addr, addr + PAGE_SIZE-1);
>  
> -	free_page((unsigned long)pte);
> +	page = virt_to_page(pte);
> +	pgtable_clear_and_dec(page);
> +	__free_page(page);
>  
>  	return 1;
>  }
> diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
> index 328a714..2e20e9e 100644
> --- a/include/asm-generic/pgalloc.h
> +++ b/include/asm-generic/pgalloc.h
> @@ -18,7 +18,14 @@
>   */
>  static inline pte_t *__pte_alloc_one_kernel(struct mm_struct *mm)
>  {
> -	return (pte_t *)__get_free_page(GFP_PGTABLE_KERNEL);
> +	struct page *page;
> +	gfp_t gfp = GFP_PGTABLE_KERNEL;
> +
> +	page = alloc_pages(gfp & ~__GFP_HIGHMEM, 0);
> +	if (!page)
> +		return NULL;
> +	pgtable_set_and_inc(page);
> +	return (pte_t *)page_address(page);

{
	pte_t *pte = (pte_t *)__get_free_page(GFP_PGTABLE_KERNEL);

	if (pte)
		pgtable_set_and_inc(virt_to_page(pte));

	return pte;
}

looks simpler, doesn't it?

>  }
>  
>  #ifndef __HAVE_ARCH_PTE_ALLOC_ONE_KERNEL
> @@ -41,7 +48,10 @@ static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
>   */
>  static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
>  {
> -	free_page((unsigned long)pte);
> +	struct page *page = virt_to_page(pte);
> +
> +	pgtable_clear_and_dec(page);
> +	__free_page(page);
>  }
>  
>  /**
> -- 
> 1.8.3.1
> 

-- 
Sincerely yours,
Mike.