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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2014-01-21 15:49:07 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-21 16:19:44 -0800
commitb35f1819acd9243a3ff7ad25b1fa8bd6bfe80fb2 (patch)
tree140f810d09226caa12531e0a02126af64e71e314 /include
parent943dca1a1fcbccb58de944669b833fd38a6c809b (diff)
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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mm.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 58202c26c559..fc4415256ec3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1350,6 +1350,7 @@ static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long a
#if USE_SPLIT_PTE_PTLOCKS
#if ALLOC_SPLIT_PTLOCKS
+void __init ptlock_cache_init(void);
extern bool ptlock_alloc(struct page *page);
extern void ptlock_free(struct page *page);
@@ -1358,6 +1359,10 @@ static inline spinlock_t *ptlock_ptr(struct page *page)
return page->ptl;
}
#else /* ALLOC_SPLIT_PTLOCKS */
+static inline void ptlock_cache_init(void)
+{
+}
+
static inline bool ptlock_alloc(struct page *page)
{
return true;
@@ -1410,10 +1415,17 @@ 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);