diff options
| -rw-r--r-- | arch/Kconfig | 8 | ||||
| -rw-r--r-- | arch/x86/Kconfig | 1 | ||||
| -rw-r--r-- | include/linux/mm_types.h | 9 | ||||
| -rw-r--r-- | mm/slub.c | 6 |
4 files changed, 16 insertions, 8 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index 2505740b81d..a2c5c077c32 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -185,4 +185,12 @@ config HAVE_RCU_TABLE_FREE config ARCH_HAVE_NMI_SAFE_CMPXCHG bool +config HAVE_ALIGNED_STRUCT_PAGE + bool + help + This makes sure that struct pages are double word aligned and that + e.g. the SLUB allocator can perform double word atomic operations + on a struct page for better performance. However selecting this + might increase the size of a struct page by a word. + source "kernel/gcov/Kconfig" diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index a150f4c35e9..5201a2c2723 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -60,6 +60,7 @@ config X86 select PERF_EVENTS select HAVE_PERF_EVENTS_NMI select ANON_INODES + select HAVE_ALIGNED_STRUCT_PAGE if SLUB && !M386 select HAVE_ARCH_KMEMCHECK select HAVE_USER_RETURN_NOTIFIER select ARCH_BINFMT_ELF_RANDOMIZE_PIE diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5b42f1b34eb..3cc3062b376 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -151,12 +151,11 @@ struct page { #endif } /* - * If another subsystem starts using the double word pairing for atomic - * operations on struct page then it must change the #if to ensure - * proper alignment of the page struct. + * The struct page can be forced to be double word aligned so that atomic ops + * on double words work. The SLUB allocator can make use of such a feature. */ -#if defined(CONFIG_SLUB) && defined(CONFIG_CMPXCHG_LOCAL) - __attribute__((__aligned__(2*sizeof(unsigned long)))) +#ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE + __aligned(2 * sizeof(unsigned long)) #endif ; diff --git a/mm/slub.c b/mm/slub.c index 5d37b5e4414..72aa8413460 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -366,7 +366,7 @@ static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page const char *n) { VM_BUG_ON(!irqs_disabled()); -#ifdef CONFIG_CMPXCHG_DOUBLE +#if defined(CONFIG_CMPXCHG_DOUBLE) && defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) if (s->flags & __CMPXCHG_DOUBLE) { if (cmpxchg_double(&page->freelist, &page->counters, freelist_old, counters_old, @@ -400,7 +400,7 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page, void *freelist_new, unsigned long counters_new, const char *n) { -#ifdef CONFIG_CMPXCHG_DOUBLE +#if defined(CONFIG_CMPXCHG_DOUBLE) && defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) if (s->flags & __CMPXCHG_DOUBLE) { if (cmpxchg_double(&page->freelist, &page->counters, freelist_old, counters_old, @@ -3014,7 +3014,7 @@ static int kmem_cache_open(struct kmem_cache *s, } } -#ifdef CONFIG_CMPXCHG_DOUBLE +#if defined(CONFIG_CMPXCHG_DOUBLE) && defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) if (system_has_cmpxchg_double() && (s->flags & SLAB_DEBUG_FLAGS) == 0) /* Enable fast mode */ s->flags |= __CMPXCHG_DOUBLE; |