Re: [PATCH] arm64: add a function to show the different types of pagetable

[Mark Rutland]

On Sat, Dec 05, 2015 at 09:35:32PM +0800, zhongjiang wrote:
> The patch is mainly to show  pagetable number of different level in the direct
> mapping. pagetable is created from pud to pte in arm64 , resulting in different
> resluts with x86. For instance, The kernel of two-level pages will produce three
> types of pagetable.
> 
> It can also be used to detect whether there is a large page spliting and merging.
> Large page will significantly reduce the TLB miss, and improve the system
> performance.
> 
> Signed-off-by: zhongjiang <zhongjiang@xxxxxxxxxx>
> ---
>  arch/arm64/include/asm/pgtable-types.h |   19 +++++++++++++++++
>  arch/arm64/mm/mmu.c                    |   12 +++++++++++
>  arch/arm64/mm/pageattr.c               |   35 ++++++++++++++++++++++++++++++++
>  3 files changed, 66 insertions(+), 0 deletions(-)

This looks identical to the last time [1] this was posted. I had open comments
[2], which have not been addressed.

In future, plase include a change log when submitting an updated patch, and
follow the usual convention for the subject prefix (e.g. PATCHvN for an updated
patch, PATCH RESEND if the patch content has not changed, etc).

Thanks,
Mark.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-December/390870.html
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-December/391008.html

> diff --git a/arch/arm64/include/asm/pgtable-types.h b/arch/arm64/include/asm/pgtable-types.h
> index 2b1bd7e..a0f58d0 100644
> --- a/arch/arm64/include/asm/pgtable-types.h
> +++ b/arch/arm64/include/asm/pgtable-types.h
> @@ -86,6 +86,25 @@ typedef pteval_t pgprot_t;
>  
>  #endif /* STRICT_MM_TYPECHECKS */
>  
> +struct seq_file;
> +extern void arch_report_meminfo(struct seq_file *m);
> +
> +enum pg_level {
> +	PG_LEVEL_NONE,
> +	PG_LEVEL_PTE,
> +	PG_LEVEL_PMD,
> +	PG_LEVEL_PUD,
> +	PG_LEVEL_NUM
> +};
> +
> +#ifdef CONFIG_PROC_FS
> +extern void update_page_count(int level, unsigned long pages);
> +extern void split_page_count(int level);
> +#else
> +static inline void update_page_count(int level, unsigned long pages) {}
> +static inline void split_page_count(int level) {}
> +#endif
> +
>  #if CONFIG_PGTABLE_LEVELS == 2
>  #include <asm-generic/pgtable-nopmd.h>
>  #elif CONFIG_PGTABLE_LEVELS == 3
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 0a7bee7..77aef0b 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -30,6 +30,7 @@
>  #include <linux/stop_machine.h>
>  #include <linux/bootmem.h>
>  
> +#include <asm/pgtable-types.h>
>  #include <asm/cputype.h>
>  #include <asm/fixmap.h>
>  #include <asm/sections.h>
> @@ -85,6 +86,7 @@ void split_pmd(pmd_t *pmd, pte_t *pte)
>  		set_pte(pte, pfn_pte(pfn, prot));
>  		pfn++;
>  	} while (pte++, i++, i < PTRS_PER_PTE);
> +	split_page_count(PG_LEVEL_PMD);
>  }
>  
>  static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
> @@ -93,6 +95,7 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
>  				  void *(*alloc)(unsigned long size))
>  {
>  	pte_t *pte;
> +	unsigned long i = 0;
>  
>  	if (pmd_none(*pmd) || pmd_sect(*pmd)) {
>  		pte = alloc(PTRS_PER_PTE * sizeof(pte_t));
> @@ -107,7 +110,9 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
>  	do {
>  		set_pte(pte, pfn_pte(pfn, prot));
>  		pfn++;
> +		i++;
>  	} while (pte++, addr += PAGE_SIZE, addr != end);
> +	update_page_count(PG_LEVEL_PTE, i);
>  }
>  
>  void split_pud(pud_t *old_pud, pmd_t *pmd)
> @@ -120,6 +125,7 @@ void split_pud(pud_t *old_pud, pmd_t *pmd)
>  		set_pmd(pmd, __pmd(addr | prot));
>  		addr += PMD_SIZE;
>  	} while (pmd++, i++, i < PTRS_PER_PMD);
> +	split_page_count(PG_LEVEL_PUD);
>  }
>  
>  static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
> @@ -129,6 +135,7 @@ static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
>  {
>  	pmd_t *pmd;
>  	unsigned long next;
> +	unsigned long i = 0;
>  
>  	/*
>  	 * Check for initial section mappings in the pgd/pud and remove them.
> @@ -159,6 +166,7 @@ static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
>  			 * Check for previous table entries created during
>  			 * boot (__create_page_tables) and flush them.
>  			 */
> +			i++;
>  			if (!pmd_none(old_pmd)) {
>  				flush_tlb_all();
>  				if (pmd_table(old_pmd)) {
> @@ -173,6 +181,7 @@ static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
>  		}
>  		phys += next - addr;
>  	} while (pmd++, addr = next, addr != end);
> +	update_page_count(PG_LEVEL_PMD, i);
>  }
>  
>  static inline bool use_1G_block(unsigned long addr, unsigned long next,
> @@ -194,6 +203,7 @@ static void alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
>  {
>  	pud_t *pud;
>  	unsigned long next;
> +	unsigned long i = 0;
>  
>  	if (pgd_none(*pgd)) {
>  		pud = alloc(PTRS_PER_PUD * sizeof(pud_t));
> @@ -220,6 +230,7 @@ static void alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
>  			 *
>  			 * Look up the old pmd table and free it.
>  			 */
> +			i++;
>  			if (!pud_none(old_pud)) {
>  				flush_tlb_all();
>  				if (pud_table(old_pud)) {
> @@ -233,6 +244,7 @@ static void alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
>  		}
>  		phys += next - addr;
>  	} while (pud++, addr = next, addr != end);
> +	update_page_count(PG_LEVEL_PUD, i);
>  }
>  
>  /*
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 7a5ff11..a8257a2 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -15,12 +15,47 @@
>  #include <linux/module.h>
>  #include <linux/sched.h>
>  
> +#include <linux/seq_file.h>
>  #include <asm/pgalloc.h>
>  #include <asm/pgtable.h>
>  #include <asm/tlbflush.h>
>  
>  #include "mm.h"
>  
> +static unsigned long direct_pages_count[PG_LEVEL_NUM];
> +
> +void update_page_count(int level, unsigned long pages)
> +{
> +	direct_pages_count[level] += pages;
> +}
> +
> +void split_page_count(int level)
> +{
> +	direct_pages_count[level]--;
> +	direct_pages_count[level-1] += PTRS_PER_PTE;
> +}
> +
> +void arch_report_meminfo(struct seq_file *m)
> +{
> +
> +	seq_printf(m, "DirectMap%ldk:     %8lu kB\n", PAGE_SIZE / SZ_1K,
> +			direct_pages_count[PG_LEVEL_PTE] * PAGE_SIZE / SZ_1K);
> +
> +#if CONFIG_PGTABLE_LEVELS == 2
> +	seq_printf(m, "DirectMap%ldM:     %8lu kB\n", PMD_SIZE / SZ_1M,
> +			direct_pages_count[PG_LEVEL_PMD] * PMD_SIZE / SZ_1K);
> +
> +#endif
> +
> +#if CONFIG_PGTABLE_LEVELS > 2
> +	seq_printf(m, "DirectMap%ldM:     %8lu kB\n", PMD_SIZE / SZ_1M,
> +			direct_pages_count[PG_LEVEL_PMD] * PMD_SIZE / SZ_1K);
> +	seq_printf(m, "DirectMap%ldG:     %8lu kB\n", PUD_SIZE / SZ_1G,
> +			direct_pages_count[PG_LEVEL_PUD] * PUD_SIZE  / SZ_1K);
> +
> +#endif
> +}
> +
>  static int update_pte_range(struct mm_struct *mm, pmd_t *pmd,
>  				unsigned long addr, unsigned long end,
>  				pgprot_t clear, pgprot_t set)
> -- 
> 1.7.7
> 
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