diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/slab.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/mm/slab.c b/mm/slab.c index b856786a3a30..909975f6e090 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -109,6 +109,7 @@ #include <linux/mutex.h> #include <linux/fault-inject.h> #include <linux/rtmutex.h> +#include <linux/reciprocal_div.h> #include <asm/cacheflush.h> #include <asm/tlbflush.h> @@ -386,6 +387,7 @@ struct kmem_cache { unsigned int shared; unsigned int buffer_size; + u32 reciprocal_buffer_size; /* 3) touched by every alloc & free from the backend */ struct kmem_list3 *nodelists[MAX_NUMNODES]; @@ -627,10 +629,17 @@ static inline void *index_to_obj(struct kmem_cache *cache, struct slab *slab, return slab->s_mem + cache->buffer_size * idx; } -static inline unsigned int obj_to_index(struct kmem_cache *cache, - struct slab *slab, void *obj) +/* + * We want to avoid an expensive divide : (offset / cache->buffer_size) + * Using the fact that buffer_size is a constant for a particular cache, + * we can replace (offset / cache->buffer_size) by + * reciprocal_divide(offset, cache->reciprocal_buffer_size) + */ +static inline unsigned int obj_to_index(const struct kmem_cache *cache, + const struct slab *slab, void *obj) { - return (unsigned)(obj - slab->s_mem) / cache->buffer_size; + u32 offset = (obj - slab->s_mem); + return reciprocal_divide(offset, cache->reciprocal_buffer_size); } /* @@ -1427,6 +1436,8 @@ void __init kmem_cache_init(void) cache_cache.buffer_size = ALIGN(cache_cache.buffer_size, cache_line_size()); + cache_cache.reciprocal_buffer_size = + reciprocal_value(cache_cache.buffer_size); for (order = 0; order < MAX_ORDER; order++) { cache_estimate(order, cache_cache.buffer_size, @@ -2313,6 +2324,7 @@ kmem_cache_create (const char *name, size_t size, size_t align, if (flags & SLAB_CACHE_DMA) cachep->gfpflags |= GFP_DMA; cachep->buffer_size = size; + cachep->reciprocal_buffer_size = reciprocal_value(size); if (flags & CFLGS_OFF_SLAB) { cachep->slabp_cache = kmem_find_general_cachep(slab_size, 0u); |