Re: [PATCH] mm: add statistics for PUD level pagetable

[Mike Rapoport]

On Mon, Sep 18, 2023 at 02:31:42PM +0800, Baolin Wang wrote:
> Recently, we found that cross-die access to pagetable pages on ARM64
> machines can cause performance fluctuations in our business. Currently,
> there are no PMU events available to track this situation on our ARM64
> machines, so an accurate pagetable accounting can help to analyze this
> issue, but now the PUD level pagetable accounting is missed.
> 
> So introducing pagetable_pud_ctor/dtor() to help to get an accurate
> PUD pagetable accounting, as well as converting the architectures with
> using generic PUD pagatable allocation to add corresponding PUD pagetable
> accounting. Moreover this patch will also mark the PUD level pagetable
> with PG_table flag, which will help to do sanity validation in unpoison_memory().
> 
> On my testing machine, I can see more pagetables statistics after the patch
> with page-types tool:
> 
> Before patch:
>         flags           page-count      MB  symbolic-flags                     long-symbolic-flags
> 0x0000000004000000           27326      106  __________________________g_________________       pgtable
> After patch:
> 0x0000000004000000           27541      107  __________________________g_________________       pgtable
> 
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>

Acked-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>

> ---
>  arch/arm64/include/asm/tlb.h         |  5 ++++-
>  arch/loongarch/include/asm/pgalloc.h |  1 +
>  arch/mips/include/asm/pgalloc.h      |  1 +
>  arch/x86/mm/pgtable.c                |  3 +++
>  include/asm-generic/pgalloc.h        |  7 ++++++-
>  include/linux/mm.h                   | 16 ++++++++++++++++
>  6 files changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
> index 2c29239d05c3..846c563689a8 100644
> --- a/arch/arm64/include/asm/tlb.h
> +++ b/arch/arm64/include/asm/tlb.h
> @@ -96,7 +96,10 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp,
>  static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pudp,
>  				  unsigned long addr)
>  {
> -	tlb_remove_ptdesc(tlb, virt_to_ptdesc(pudp));
> +	struct ptdesc *ptdesc = virt_to_ptdesc(pudp);
> +
> +	pagetable_pud_dtor(ptdesc);
> +	tlb_remove_ptdesc(tlb, ptdesc);
>  }
>  #endif
>  
> diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
> index 79470f0b4f1d..4e2d6b7ca2ee 100644
> --- a/arch/loongarch/include/asm/pgalloc.h
> +++ b/arch/loongarch/include/asm/pgalloc.h
> @@ -84,6 +84,7 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
>  
>  	if (!ptdesc)
>  		return NULL;
> +	pagetable_pud_ctor(ptdesc);
>  	pud = ptdesc_address(ptdesc);
>  
>  	pud_init(pud);
> diff --git a/arch/mips/include/asm/pgalloc.h b/arch/mips/include/asm/pgalloc.h
> index 40e40a7eb94a..f4440edcd8fe 100644
> --- a/arch/mips/include/asm/pgalloc.h
> +++ b/arch/mips/include/asm/pgalloc.h
> @@ -95,6 +95,7 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
>  
>  	if (!ptdesc)
>  		return NULL;
> +	pagetable_pud_ctor(ptdesc);
>  	pud = ptdesc_address(ptdesc);
>  
>  	pud_init(pud);
> diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> index 9deadf517f14..0cbc1b8e8e3d 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -76,6 +76,9 @@ void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
>  #if CONFIG_PGTABLE_LEVELS > 3
>  void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
>  {
> +	struct ptdesc *ptdesc = virt_to_ptdesc(pud);
> +
> +	pagetable_pud_dtor(ptdesc);
>  	paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
>  	paravirt_tlb_remove_table(tlb, virt_to_page(pud));
>  }
> diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
> index c75d4a753849..879e5f8aa5e9 100644
> --- a/include/asm-generic/pgalloc.h
> +++ b/include/asm-generic/pgalloc.h
> @@ -169,6 +169,8 @@ static inline pud_t *__pud_alloc_one(struct mm_struct *mm, unsigned long addr)
>  	ptdesc = pagetable_alloc(gfp, 0);
>  	if (!ptdesc)
>  		return NULL;
> +
> +	pagetable_pud_ctor(ptdesc);
>  	return ptdesc_address(ptdesc);
>  }
>  
> @@ -190,8 +192,11 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
>  
>  static inline void __pud_free(struct mm_struct *mm, pud_t *pud)
>  {
> +	struct ptdesc *ptdesc = virt_to_ptdesc(pud);
> +
>  	BUG_ON((unsigned long)pud & (PAGE_SIZE-1));
> -	pagetable_free(virt_to_ptdesc(pud));
> +	pagetable_pud_dtor(ptdesc);
> +	pagetable_free(ptdesc);
>  }
>  
>  #ifndef __HAVE_ARCH_PUD_FREE
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 12335de50140..2232bfebb88a 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3049,6 +3049,22 @@ static inline spinlock_t *pud_lock(struct mm_struct *mm, pud_t *pud)
>  	return ptl;
>  }
>  
> +static inline void pagetable_pud_ctor(struct ptdesc *ptdesc)
> +{
> +	struct folio *folio = ptdesc_folio(ptdesc);
> +
> +	__folio_set_pgtable(folio);
> +	lruvec_stat_add_folio(folio, NR_PAGETABLE);
> +}
> +
> +static inline void pagetable_pud_dtor(struct ptdesc *ptdesc)
> +{
> +	struct folio *folio = ptdesc_folio(ptdesc);
> +
> +	__folio_clear_pgtable(folio);
> +	lruvec_stat_sub_folio(folio, NR_PAGETABLE);
> +}
> +
>  extern void __init pagecache_init(void);
>  extern void free_initmem(void);
>  
> -- 
> 2.39.3
> 
> 

-- 
Sincerely yours,
Mike.