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>
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@ -971,7 +971,7 @@ EXPORT_SYMBOL(kmalloc_dma_caches);
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* of two cache sizes there. The size of larger slabs can be determined using
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* fls.
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*/
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static s8 size_index[24] __ro_after_init = {
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static u8 size_index[24] __ro_after_init = {
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3, /* 8 */
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4, /* 16 */
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5, /* 24 */
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@ -1009,7 +1009,7 @@ static inline int size_index_elem(size_t bytes)
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*/
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struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags)
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{
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int index;
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unsigned int index;
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if (unlikely(size > KMALLOC_MAX_SIZE)) {
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WARN_ON_ONCE(!(flags & __GFP_NOWARN));
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