[PATCH -v2 08/10] m68k,mm: Extend table allocator for multiple sizes

Peter Zijlstra
2020-01-31T12:56:38Z

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;
}