From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: 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@xxxxxxxxx Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx> Acked-by: Christoph Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slab_common.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff -puN mm/slab_common.c~slab-make-size_index-array-u8 mm/slab_common.c --- a/mm/slab_common.c~slab-make-size_index-array-u8 +++ a/mm/slab_common.c @@ -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 */ 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)); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
