slab: make size_index[] array u8
All those small numbers are reverse indexes into kmalloc caches array
and can't be negative.
On x86_64 "unsigned int = fls()" can drop CDQE instruction:
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-2 (-2)
Function old new delta
kmalloc_slab 101 99 -2
Link: http://lkml.kernel.org/r/20180305200730.15812-7-adobriyan@gmail.com
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slab_common.c b/mm/slab_common.c
index a4545a6..dda966e 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -971,7 +971,7 @@
* of two cache sizes there. The size of larger slabs can be determined using
* fls.
*/
-static s8 size_index[24] __ro_after_init = {
+static u8 size_index[24] __ro_after_init = {
3, /* 8 */
4, /* 16 */
5, /* 24 */
@@ -1009,7 +1009,7 @@
*/
struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags)
{
- int index;
+ unsigned int index;
if (unlikely(size > KMALLOC_MAX_SIZE)) {
WARN_ON_ONCE(!(flags & __GFP_NOWARN));