Skip to content

Commit

Permalink
mm: create a separate slab for page->ptl allocation
Browse files Browse the repository at this point in the history
If DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC are enabled spinlock_t on x86_64
is 72 bytes.  For page->ptl they will be allocated from kmalloc-96 slab,
so we loose 24 on each.  An average system can easily allocate few tens
thousands of page->ptl and overhead is significant.

Let's create a separate slab for page->ptl allocation to solve this.

Signed-off-by: Kirill A. Shutemov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
  • Loading branch information
kiryl authored and torvalds committed Nov 15, 2013
1 parent 539edb5 commit ea1e7ed
Show file tree
Hide file tree
Showing 3 changed files with 17 additions and 1 deletion.
9 changes: 9 additions & 0 deletions include/linux/mm.h
Original file line number Diff line number Diff line change
Expand Up @@ -1318,6 +1318,7 @@ static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long a

#if USE_SPLIT_PTE_PTLOCKS
#if BLOATED_SPINLOCKS
void __init ptlock_cache_init(void);
extern bool ptlock_alloc(struct page *page);
extern void ptlock_free(struct page *page);

Expand All @@ -1326,6 +1327,7 @@ static inline spinlock_t *ptlock_ptr(struct page *page)
return page->ptl;
}
#else /* BLOATED_SPINLOCKS */
static inline void ptlock_cache_init(void) {}
static inline bool ptlock_alloc(struct page *page)
{
return true;
Expand Down Expand Up @@ -1378,10 +1380,17 @@ static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
{
return &mm->page_table_lock;
}
static inline void ptlock_cache_init(void) {}
static inline bool ptlock_init(struct page *page) { return true; }
static inline void pte_lock_deinit(struct page *page) {}
#endif /* USE_SPLIT_PTE_PTLOCKS */

static inline void pgtable_init(void)
{
ptlock_cache_init();
pgtable_cache_init();
}

static inline bool pgtable_page_ctor(struct page *page)
{
inc_zone_page_state(page, NR_PAGETABLE);
Expand Down
2 changes: 1 addition & 1 deletion init/main.c
Original file line number Diff line number Diff line change
Expand Up @@ -473,7 +473,7 @@ static void __init mm_init(void)
mem_init();
kmem_cache_init();
percpu_init_late();
pgtable_cache_init();
pgtable_init();
vmalloc_init();
}

Expand Down
7 changes: 7 additions & 0 deletions mm/memory.c
Original file line number Diff line number Diff line change
Expand Up @@ -4272,6 +4272,13 @@ void copy_user_huge_page(struct page *dst, struct page *src,
#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */

#if USE_SPLIT_PTE_PTLOCKS && BLOATED_SPINLOCKS
static struct kmem_cache *page_ptl_cachep;
void __init ptlock_cache_init(void)
{
page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0,
SLAB_PANIC, NULL);
}

bool ptlock_alloc(struct page *page)
{
spinlock_t *ptl;
Expand Down

0 comments on commit ea1e7ed

Please sign in to comment.