Commit d5f86655 authored Apr 05, 2018 by Alexey Dobriyan Committed by Linus Torvalds Apr 05, 2018

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>

parent f4957d5b

mm/slab_common.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -971,7 +971,7 @@ EXPORT_SYMBOL(kmalloc_dma_caches);
		* 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 @@ static inline int size_index_elem(size_t bytes)
		*/
		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));

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