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-rw-r--r--mm/slab.c81
1 files changed, 59 insertions, 22 deletions
diff --git a/mm/slab.c b/mm/slab.c
index 613d385519fe..e869400ea731 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -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)