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mm: create a separate slab for page->ptl allocation
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. To make sure that it really works this time, some numbers from my test machine (just booted, no load): Before: # grep '^\(kmalloc-96\|page->ptl\)' /proc/slabinfo kmalloc-96 31987 32190 128 30 1 : tunables 120 60 8 : slabdata 1073 1073 92 After: # grep '^\(kmalloc-96\|page->ptl\)' /proc/slabinfo page->ptl 27516 28143 72 53 1 : tunables 120 60 8 : slabdata 531 531 9 kmalloc-96 3853 5280 128 30 1 : tunables 120 60 8 : slabdata 176 176 0 Note that the patch is useful not only for debug case, but also for PREEMPT_RT, where spinlock_t is always bloated. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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3 changed files with 24 additions and 3 deletions
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@ -1350,6 +1350,7 @@ static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long a
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#if USE_SPLIT_PTE_PTLOCKS
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#if ALLOC_SPLIT_PTLOCKS
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void __init ptlock_cache_init(void);
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extern bool ptlock_alloc(struct page *page);
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extern void ptlock_free(struct page *page);
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@ -1358,6 +1359,10 @@ static inline spinlock_t *ptlock_ptr(struct page *page)
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return page->ptl;
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}
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#else /* ALLOC_SPLIT_PTLOCKS */
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static inline void ptlock_cache_init(void)
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{
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}
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static inline bool ptlock_alloc(struct page *page)
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{
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return true;
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@ -1410,10 +1415,17 @@ static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
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{
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return &mm->page_table_lock;
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}
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static inline void ptlock_cache_init(void) {}
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static inline bool ptlock_init(struct page *page) { return true; }
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static inline void pte_lock_deinit(struct page *page) {}
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#endif /* USE_SPLIT_PTE_PTLOCKS */
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static inline void pgtable_init(void)
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{
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ptlock_cache_init();
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pgtable_cache_init();
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}
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static inline bool pgtable_page_ctor(struct page *page)
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{
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inc_zone_page_state(page, NR_PAGETABLE);
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@ -476,7 +476,7 @@ static void __init mm_init(void)
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mem_init();
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kmem_cache_init();
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percpu_init_late();
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pgtable_cache_init();
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pgtable_init();
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vmalloc_init();
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}
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13
mm/memory.c
13
mm/memory.c
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@ -4275,11 +4275,20 @@ void copy_user_huge_page(struct page *dst, struct page *src,
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
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#if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS
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static struct kmem_cache *page_ptl_cachep;
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void __init ptlock_cache_init(void)
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{
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page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0,
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SLAB_PANIC, NULL);
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}
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bool ptlock_alloc(struct page *page)
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{
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spinlock_t *ptl;
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ptl = kmalloc(sizeof(spinlock_t), GFP_KERNEL);
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ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL);
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if (!ptl)
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return false;
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page->ptl = ptl;
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@ -4288,6 +4297,6 @@ bool ptlock_alloc(struct page *page)
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void ptlock_free(struct page *page)
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{
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kfree(page->ptl);
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kmem_cache_free(page_ptl_cachep, page->ptl);
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}
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#endif
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