mm/sl[aou]b: Common alignment code
Extract the code to do object alignment from the allocators.
Do the alignment calculations in slab_common so that the
__kmem_cache_create functions of the allocators do not have
to deal with alignment.
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 497b45c..a8e76d7 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -73,6 +73,34 @@
#endif
/*
+ * Figure out what the alignment of the objects will be given a set of
+ * flags, a user specified alignment and the size of the objects.
+ */
+unsigned long calculate_alignment(unsigned long flags,
+ unsigned long align, unsigned long size)
+{
+ /*
+ * If the user wants hardware cache aligned objects then follow that
+ * suggestion if the object is sufficiently large.
+ *
+ * The hardware cache alignment cannot override the specified
+ * alignment though. If that is greater then use it.
+ */
+ if (flags & SLAB_HWCACHE_ALIGN) {
+ unsigned long ralign = cache_line_size();
+ while (size <= ralign / 2)
+ ralign /= 2;
+ align = max(align, ralign);
+ }
+
+ if (align < ARCH_SLAB_MINALIGN)
+ align = ARCH_SLAB_MINALIGN;
+
+ return ALIGN(align, sizeof(void *));
+}
+
+
+/*
* kmem_cache_create - Create a cache.
* @name: A string which is used in /proc/slabinfo to identify this cache.
* @size: The size of objects to be created in this cache.
@@ -124,7 +152,7 @@
s = kmem_cache_zalloc(kmem_cache, GFP_KERNEL);
if (s) {
s->object_size = s->size = size;
- s->align = align;
+ s->align = calculate_alignment(flags, align, size);
s->ctor = ctor;
s->name = kstrdup(name, GFP_KERNEL);
if (!s->name) {
@@ -211,7 +239,7 @@
s->name = name;
s->size = s->object_size = size;
- s->align = ARCH_KMALLOC_MINALIGN;
+ s->align = calculate_alignment(flags, ARCH_KMALLOC_MINALIGN, size);
err = __kmem_cache_create(s, flags);
if (err)