Provide a method to get the upper bound on the pages needed to allocate a given number of objects from a given kmem_cache. This lays the foundation for a generic reserve framework as presented in a later patch in this series. This framework needs to convert object demand (kmalloc() bytes, kmem_cache_alloc() objects) to pages. Signed-off-by: Peter Zijlstra --- include/linux/slab.h | 4 ++ mm/slab.c | 75 +++++++++++++++++++++++++++++++++++++++++++++ mm/slub.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 163 insertions(+) Index: linux-2.6/include/linux/slab.h =================================================================== --- linux-2.6.orig/include/linux/slab.h +++ linux-2.6/include/linux/slab.h @@ -60,6 +60,8 @@ void kmem_cache_free(struct kmem_cache * unsigned int kmem_cache_size(struct kmem_cache *); const char *kmem_cache_name(struct kmem_cache *); int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr); +unsigned kmem_alloc_estimate(struct kmem_cache *cachep, + gfp_t flags, int objects); /* * Please use this macro to create slab caches. Simply specify the @@ -94,6 +96,8 @@ int kmem_ptr_validate(struct kmem_cache void * __must_check krealloc(const void *, size_t, gfp_t); void kfree(const void *); size_t ksize(const void *); +unsigned kmalloc_estimate_fixed(size_t, gfp_t, int); +unsigned kmalloc_estimate_variable(gfp_t, size_t); /* * Allocator specific definitions. These are mainly used to establish optimized Index: linux-2.6/mm/slub.c =================================================================== --- linux-2.6.orig/mm/slub.c +++ linux-2.6/mm/slub.c @@ -2347,6 +2347,39 @@ const char *kmem_cache_name(struct kmem_ EXPORT_SYMBOL(kmem_cache_name); /* + * Calculate the upper bound of pages required to sequentially allocate + * @objects objects from @cachep. + * + * We should use s->min_objects because those are the least efficient. + */ +unsigned kmem_alloc_estimate(struct kmem_cache *s, gfp_t flags, int objects) +{ + unsigned long pages; + + if (WARN_ON(!s) || WARN_ON(!s->min_objects)) + return 0; + + pages = DIV_ROUND_UP(objects, s->min_objects) << get_order(s->size); + + /* + * Account the possible additional overhead if the slab holds more that + * one object. Use s->max_objects because that's the worst case. + */ + if (s->max_objects > 1) { + /* + * Account the possible additional overhead if per cpu slabs + * are currently empty and have to be allocated. This is very + * unlikely but a possible scenario immediately after + * kmem_cache_shrink. + */ + pages += num_online_cpus() << s->order; + } + + return pages; +} +EXPORT_SYMBOL_GPL(kmem_alloc_estimate); + +/* * Attempt to free all slabs on a node. Return the number of slabs we * were unable to free. */ @@ -2726,6 +2759,57 @@ static unsigned long count_partial_total } /* + * Calculate the upper bound of pages required to sequentially allocate + * @count objects of @size bytes from kmalloc given @flags. + */ +unsigned kmalloc_estimate_fixed(size_t size, gfp_t flags, int count) +{ + struct kmem_cache *s = get_slab(size, flags); + if (!s) + return 0; + + return kmem_alloc_estimate(s, flags, count); + +} +EXPORT_SYMBOL_GPL(kmalloc_estimate_fixed); + +/* + * Calculate the upper bound of pages requires to sequentially allocate @bytes + * from kmalloc in an unspecified number of allocations of nonuniform size. + */ +unsigned kmalloc_estimate_variable(gfp_t flags, size_t bytes) +{ + int i; + unsigned long pages; + + /* + * multiply by two, in order to account the worst case slack space + * due to the power-of-two allocation sizes. + */ + pages = DIV_ROUND_UP(2 * bytes, PAGE_SIZE); + + /* + * add the kmem_cache overhead of each possible kmalloc cache + */ + for (i = 1; i < PAGE_SHIFT; i++) { + struct kmem_cache *s; + +#ifdef CONFIG_ZONE_DMA + if (unlikely(flags & SLUB_DMA)) + s = dma_kmalloc_cache(i, flags); + else +#endif + s = &kmalloc_caches[i]; + + if (s) + pages += kmem_alloc_estimate(s, flags, 0); + } + + return pages; +} +EXPORT_SYMBOL_GPL(kmalloc_estimate_variable); + +/* * kmem_cache_shrink removes empty slabs from the partial lists and sorts * the remaining slabs by the number of items in use. The slabs with the * most items in use come first. New allocations will then fill those up Index: linux-2.6/mm/slab.c =================================================================== --- linux-2.6.orig/mm/slab.c +++ linux-2.6/mm/slab.c @@ -3847,6 +3847,81 @@ const char *kmem_cache_name(struct kmem_ EXPORT_SYMBOL_GPL(kmem_cache_name); /* + * Calculate the upper bound of pages required to sequentially allocate + * @objects objects from @cachep. + */ +unsigned kmem_alloc_estimate(struct kmem_cache *cachep, + gfp_t flags, int objects) +{ + /* + * (1) memory for objects, + */ + unsigned nr_slabs = DIV_ROUND_UP(objects, cachep->num); + unsigned nr_pages = nr_slabs << cachep->gfporder; + + /* + * (2) memory for each per-cpu queue (nr_cpu_ids), + * (3) memory for each per-node alien queues (nr_cpu_ids), and + * (4) some amount of memory for the slab management structures + * + * XXX: truely account these + */ + nr_pages += 1 + ilog2(nr_pages); + + return nr_pages; +} + +/* + * Calculate the upper bound of pages required to sequentially allocate + * @count objects of @size bytes from kmalloc given @flags. + */ +unsigned kmalloc_estimate_fixed(size_t size, gfp_t flags, int count) +{ + struct kmem_cache *s = kmem_find_general_cachep(size, flags); + if (!s) + return 0; + + return kmem_alloc_estimate(s, flags, count); +} +EXPORT_SYMBOL_GPL(kmalloc_estimate_fixed); + +/* + * Calculate the upper bound of pages requires to sequentially allocate @bytes + * from kmalloc in an unspecified number of allocations of nonuniform size. + */ +unsigned kmalloc_estimate_variable(gfp_t flags, size_t bytes) +{ + unsigned long pages; + struct cache_sizes *csizep = malloc_sizes; + + /* + * multiply by two, in order to account the worst case slack space + * due to the power-of-two allocation sizes. + */ + pages = DIV_ROUND_UP(2 * bytes, PAGE_SIZE); + + /* + * add the kmem_cache overhead of each possible kmalloc cache + */ + for (csizep = malloc_sizes; csizep->cs_cachep; csizep++) { + struct kmem_cache *s; + +#ifdef CONFIG_ZONE_DMA + if (unlikely(flags & __GFP_DMA)) + s = csizep->cs_dmacachep; + else +#endif + s = csizep->cs_cachep; + + if (s) + pages += kmem_alloc_estimate(s, flags, 0); + } + + return pages; +} +EXPORT_SYMBOL_GPL(kmalloc_estimate_variable); + +/* * This initializes kmem_list3 or resizes various caches for all nodes. */ static int alloc_kmemlist(struct kmem_cache *cachep) -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/