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    Subject[PATCH -v2 08/10] m68k,mm: Extend table allocator for multiple sizes
    In addition to the PGD/PMD table size (128*4) add a PTE table size
    (64*4) to the table allocator. This completely removes the pte-table
    overhead compared to the old code, even for dense tables.

    Notes:

    - the allocator gained a list_empty() check to deal with there not
    being any pages at all.

    - the free mask is extended to cover more than the 8 bits required
    for the (512 byte) PGD/PMD tables.

    - NR_PAGETABLE accounting is restored.

    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    ---
    arch/m68k/include/asm/motorola_pgalloc.h | 31 +++++++++-----
    arch/m68k/mm/init.c | 16 +++----
    arch/m68k/mm/motorola.c | 65 ++++++++++++++++++++-----------
    3 files changed, 70 insertions(+), 42 deletions(-)

    --- a/arch/m68k/include/asm/motorola_pgalloc.h
    +++ b/arch/m68k/include/asm/motorola_pgalloc.h
    @@ -8,61 +8,68 @@
    extern void mmu_page_ctor(void *page);
    extern void mmu_page_dtor(void *page);

    -extern pmd_t *get_pointer_table(void);
    -extern int free_pointer_table(pmd_t *);
    +enum m68k_table_types {
    + TABLE_PGD = 0,
    + TABLE_PMD = 0, /* same size as PGD */
    + TABLE_PTE = 1,
    +};
    +
    +extern void init_pointer_table(void *table, int type);
    +extern void *get_pointer_table(int type);
    +extern int free_pointer_table(void *table, int type);

    static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
    {
    - return (pte_t *)get_pointer_table();
    + return get_pointer_table(TABLE_PTE);
    }

    static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
    {
    - free_pointer_table((void *)pte);
    + free_pointer_table(pte, TABLE_PTE);
    }

    static inline pgtable_t pte_alloc_one(struct mm_struct *mm)
    {
    - return (pte_t *)get_pointer_table();
    + return get_pointer_table(TABLE_PTE);
    }

    static inline void pte_free(struct mm_struct *mm, pgtable_t pgtable)
    {
    - free_pointer_table((void *)pgtable);
    + free_pointer_table(pgtable, TABLE_PTE);
    }

    static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pgtable,
    unsigned long address)
    {
    - free_pointer_table((void *)pgtable);
    + free_pointer_table(pgtable, TABLE_PTE);
    }


    static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
    {
    - return get_pointer_table();
    + return get_pointer_table(TABLE_PMD);
    }

    static inline int pmd_free(struct mm_struct *mm, pmd_t *pmd)
    {
    - return free_pointer_table(pmd);
    + return free_pointer_table(pmd, TABLE_PMD);
    }

    static inline int __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd,
    unsigned long address)
    {
    - return free_pointer_table(pmd);
    + return free_pointer_table(pmd, TABLE_PMD);
    }


    static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
    {
    - pmd_free(mm, (pmd_t *)pgd);
    + free_pointer_table(pgd, TABLE_PGD);
    }

    static inline pgd_t *pgd_alloc(struct mm_struct *mm)
    {
    - return (pgd_t *)get_pointer_table();
    + return get_pointer_table(TABLE_PGD);
    }


    --- a/arch/m68k/mm/init.c
    +++ b/arch/m68k/mm/init.c
    @@ -40,10 +40,6 @@
    void *empty_zero_page;
    EXPORT_SYMBOL(empty_zero_page);

    -#if !defined(CONFIG_SUN3) && !defined(CONFIG_COLDFIRE)
    -extern void init_pointer_table(unsigned long ptable);
    -#endif
    -
    #ifdef CONFIG_MMU

    pg_data_t pg_data_map[MAX_NUMNODES];
    @@ -127,12 +123,16 @@ static inline void init_pointer_tables(v
    int i;

    /* insert pointer tables allocated so far into the tablelist */
    - init_pointer_table((unsigned long)kernel_pg_dir);
    + init_pointer_table(kernel_pg_dir, TABLE_PGD);
    for (i = 0; i < PTRS_PER_PGD; i++) {
    - pud_t *pud = (pud_t *)(&kernel_pg_dir[i]);
    + pud_t *pud = (pud_t *)&kernel_pg_dir[i];
    + pmd_t *pmd_dir;
    +
    + if (!pud_present(*pud))
    + continue;

    - if (pud_present(*pud))
    - init_pointer_table(pgd_page_vaddr(kernel_pg_dir[i]));
    + pmd_dir = (pmd_t *)pgd_page_vaddr(kernel_pg_dir[i]);
    + init_pointer_table(pmd_dir, TABLE_PMD);
    }
    #endif
    }
    --- a/arch/m68k/mm/motorola.c
    +++ b/arch/m68k/mm/motorola.c
    @@ -72,24 +72,35 @@ void mmu_page_dtor(void *page)
    arch/sparc/mm/srmmu.c ... */

    typedef struct list_head ptable_desc;
    -static LIST_HEAD(ptable_list);
    +
    +static struct list_head ptable_list[2] = {
    + LIST_HEAD_INIT(ptable_list[0]),
    + LIST_HEAD_INIT(ptable_list[1]),
    +};

    #define PD_PTABLE(page) ((ptable_desc *)&(virt_to_page(page)->lru))
    #define PD_PAGE(ptable) (list_entry(ptable, struct page, lru))
    -#define PD_MARKBITS(dp) (*(unsigned char *)&PD_PAGE(dp)->index)
    +#define PD_MARKBITS(dp) (*(unsigned int *)&PD_PAGE(dp)->index)
    +
    +static const int ptable_shift[2] = {
    + 7+2, /* PGD, PMD */
    + 6+2, /* PTE */
    +};

    -#define PTABLE_SIZE (PTRS_PER_PMD * sizeof(pmd_t))
    +#define ptable_size(type) (1U << ptable_shift[type])
    +#define ptable_mask(type) ((1U << (PAGE_SIZE / ptable_size(type))) - 1)

    -void __init init_pointer_table(unsigned long ptable)
    +void __init init_pointer_table(void *table, int type)
    {
    ptable_desc *dp;
    + unsigned long ptable = (unsigned long)table;
    unsigned long page = ptable & PAGE_MASK;
    - unsigned char mask = 1 << ((ptable - page)/PTABLE_SIZE);
    + unsigned int mask = 1U << ((ptable - page)/ptable_size(type));

    dp = PD_PTABLE(page);
    if (!(PD_MARKBITS(dp) & mask)) {
    - PD_MARKBITS(dp) = 0xff;
    - list_add(dp, &ptable_list);
    + PD_MARKBITS(dp) = ptable_mask(type);
    + list_add(dp, &ptable_list[type]);
    }

    PD_MARKBITS(dp) &= ~mask;
    @@ -102,12 +113,11 @@ void __init init_pointer_table(unsigned
    return;
    }

    -pmd_t *get_pointer_table (void)
    +void *get_pointer_table(int type)
    {
    - ptable_desc *dp = ptable_list.next;
    - unsigned char mask = PD_MARKBITS (dp);
    - unsigned char tmp;
    - unsigned int off;
    + ptable_desc *dp = ptable_list[type].next;
    + unsigned int mask = list_empty(&ptable_list[type]) ? 0 : PD_MARKBITS(dp);
    + unsigned int tmp, off;

    /*
    * For a pointer table for a user process address space, a
    @@ -122,30 +132,39 @@ pmd_t *get_pointer_table (void)
    if (!(page = (void *)get_zeroed_page(GFP_KERNEL)))
    return NULL;

    + if (type == TABLE_PTE) {
    + /*
    + * m68k doesn't have SPLIT_PTE_PTLOCKS for not having
    + * SMP.
    + */
    + pgtable_pte_page_ctor(virt_to_page(page));
    + }
    +
    mmu_page_ctor(page);

    new = PD_PTABLE(page);
    - PD_MARKBITS(new) = 0xfe;
    + PD_MARKBITS(new) = ptable_mask(type) - 1;
    list_add_tail(new, dp);

    return (pmd_t *)page;
    }

    - for (tmp = 1, off = 0; (mask & tmp) == 0; tmp <<= 1, off += PTABLE_SIZE)
    + for (tmp = 1, off = 0; (mask & tmp) == 0; tmp <<= 1, off += ptable_size(type))
    ;
    PD_MARKBITS(dp) = mask & ~tmp;
    if (!PD_MARKBITS(dp)) {
    /* move to end of list */
    - list_move_tail(dp, &ptable_list);
    + list_move_tail(dp, &ptable_list[type]);
    }
    - return (pmd_t *) (page_address(PD_PAGE(dp)) + off);
    + return page_address(PD_PAGE(dp)) + off;
    }

    -int free_pointer_table (pmd_t *ptable)
    +int free_pointer_table(void *table, int type)
    {
    ptable_desc *dp;
    - unsigned long page = (unsigned long)ptable & PAGE_MASK;
    - unsigned char mask = 1 << (((unsigned long)ptable - page)/PTABLE_SIZE);
    + unsigned long ptable = (unsigned long)table;
    + unsigned long page = ptable & PAGE_MASK;
    + unsigned int mask = 1U << ((ptable - page)/ptable_size(type));

    dp = PD_PTABLE(page);
    if (PD_MARKBITS (dp) & mask)
    @@ -153,18 +172,20 @@ int free_pointer_table (pmd_t *ptable)

    PD_MARKBITS (dp) |= mask;

    - if (PD_MARKBITS(dp) == 0xff) {
    + if (PD_MARKBITS(dp) == ptable_mask(type)) {
    /* all tables in page are free, free page */
    list_del(dp);
    mmu_page_dtor((void *)page);
    + if (type == TABLE_PTE)
    + pgtable_pte_page_dtor(virt_to_page(page));
    free_page (page);
    return 1;
    - } else if (ptable_list.next != dp) {
    + } else if (ptable_list[type].next != dp) {
    /*
    * move this descriptor to the front of the list, since
    * it has one or more free tables.
    */
    - list_move(dp, &ptable_list);
    + list_move(dp, &ptable_list[type]);
    }
    return 0;
    }

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