diff options
| -rw-r--r-- | mm/slab.c | 81 |
1 files changed, 59 insertions, 22 deletions
@@ -702,32 +702,69 @@ kmem_cache_t *kmem_find_general_cachep(size_t size, gfp_t gfpflags) } EXPORT_SYMBOL(kmem_find_general_cachep); -/* Cal the num objs, wastage, and bytes left over for a given slab size. */ -static void cache_estimate(unsigned long gfporder, size_t size, size_t align, - int flags, size_t *left_over, unsigned int *num) +static size_t slab_mgmt_size(size_t nr_objs, size_t align) { - int i; - size_t wastage = PAGE_SIZE << gfporder; - size_t extra = 0; - size_t base = 0; + return ALIGN(sizeof(struct slab)+nr_objs*sizeof(kmem_bufctl_t), align); +} - if (!(flags & CFLGS_OFF_SLAB)) { - base = sizeof(struct slab); - extra = sizeof(kmem_bufctl_t); - } - i = 0; - while (i * size + ALIGN(base + i * extra, align) <= wastage) - i++; - if (i > 0) - i--; +/* Calculate the number of objects and left-over bytes for a given + buffer size. */ +static void cache_estimate(unsigned long gfporder, size_t buffer_size, + size_t align, int flags, size_t *left_over, + unsigned int *num) +{ + int nr_objs; + size_t mgmt_size; + size_t slab_size = PAGE_SIZE << gfporder; - if (i > SLAB_LIMIT) - i = SLAB_LIMIT; + /* + * The slab management structure can be either off the slab or + * on it. For the latter case, the memory allocated for a + * slab is used for: + * + * - The struct slab + * - One kmem_bufctl_t for each object + * - Padding to respect alignment of @align + * - @buffer_size bytes for each object + * + * If the slab management structure is off the slab, then the + * alignment will already be calculated into the size. Because + * the slabs are all pages aligned, the objects will be at the + * correct alignment when allocated. + */ + if (flags & CFLGS_OFF_SLAB) { + mgmt_size = 0; + nr_objs = slab_size / buffer_size; - *num = i; - wastage -= i * size; - wastage -= ALIGN(base + i * extra, align); - *left_over = wastage; + if (nr_objs > SLAB_LIMIT) + nr_objs = SLAB_LIMIT; + } else { + /* + * Ignore padding for the initial guess. The padding + * is at most @align-1 bytes, and @buffer_size is at + * least @align. In the worst case, this result will + * be one greater than the number of objects that fit + * into the memory allocation when taking the padding + * into account. + */ + nr_objs = (slab_size - sizeof(struct slab)) / + (buffer_size + sizeof(kmem_bufctl_t)); + + /* + * This calculated number will be either the right + * amount, or one greater than what we want. + */ + if (slab_mgmt_size(nr_objs, align) + nr_objs*buffer_size + > slab_size) + nr_objs--; + + if (nr_objs > SLAB_LIMIT) + nr_objs = SLAB_LIMIT; + + mgmt_size = slab_mgmt_size(nr_objs, align); + } + *num = nr_objs; + *left_over = slab_size - nr_objs*buffer_size - mgmt_size; } #define slab_error(cachep, msg) __slab_error(__FUNCTION__, cachep, msg) |
