On Sun, Aug 28, 2022 at 11:14:48PM +0800, Dawei Li wrote: > Current size2index is implemented by one to one hardcode mapping, > which can be improved by order_base_2(). > Must be careful to not violate compile-time optimization rule. > Generated code for caller of kmalloc: > 48 8b 3d 9f 0b 6b 01 mov 0x16b0b9f(%rip),%rdi > # ffffffff826d1568 <kmalloc_caches+0x48> > ba 08 01 00 00 mov $0x108,%edx > be c0 0d 00 00 mov $0xdc0,%esi > e8 98 d7 2e 00 callq ffffffff8130e170 <kmem_cache_alloc_trace> > > Signed-off-by: Dawei Li <set_pte_at@xxxxxxxxxxx> > --- > include/linux/slab.h | 34 +++++++++------------------------- > 1 file changed, 9 insertions(+), 25 deletions(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index 0fefdf528e0d..66452a4357c6 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -17,7 +17,7 @@ > #include <linux/types.h> > #include <linux/workqueue.h> > #include <linux/percpu-refcount.h> > - > +#include <linux/log2.h> > > /* > * Flags to pass to kmem_cache_create(). > @@ -394,31 +394,16 @@ static __always_inline unsigned int __kmalloc_index(size_t size, > > if (KMALLOC_MIN_SIZE <= 32 && size > 64 && size <= 96) > return 1; > + > if (KMALLOC_MIN_SIZE <= 64 && size > 128 && size <= 192) > return 2; > - if (size <= 8) return 3; > - if (size <= 16) return 4; > - if (size <= 32) return 5; > - if (size <= 64) return 6; > - if (size <= 128) return 7; > - if (size <= 256) return 8; > - if (size <= 512) return 9; > - if (size <= 1024) return 10; > - if (size <= 2 * 1024) return 11; > - if (size <= 4 * 1024) return 12; > - if (size <= 8 * 1024) return 13; > - if (size <= 16 * 1024) return 14; > - if (size <= 32 * 1024) return 15; > - if (size <= 64 * 1024) return 16; > - if (size <= 128 * 1024) return 17; > - if (size <= 256 * 1024) return 18; > - if (size <= 512 * 1024) return 19; > - if (size <= 1024 * 1024) return 20; > - if (size <= 2 * 1024 * 1024) return 21; > - if (size <= 4 * 1024 * 1024) return 22; > - if (size <= 8 * 1024 * 1024) return 23; > - if (size <= 16 * 1024 * 1024) return 24; > - if (size <= 32 * 1024 * 1024) return 25; It does not apply. better rebase it on Vlastimil's slab tree (for-next branch) https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git/ > + > + if (size <= 8) > + return 3; > + > + /* Following compile-time optimization rule is mandatory. */ > + if (size <= 32 * 1024 * 1024) > + return order_base_2(size); Oh, it seems order_base_2() does compile-time opitmization as well. With order_base_2(), what about using KMALLOC_MAX_CACHE_SIZE instead of 32 * 1024 * 1024? I think that would be more robust. Hmm also better check if it works okay with kfence tests (it passes non-constant value) let't check if it breaks after rebase. Thanks! > > if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) > BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); > @@ -700,7 +685,6 @@ static inline __alloc_size(1, 2) void *kcalloc_node(size_t n, size_t size, gfp_t > return kmalloc_array_node(n, size, flags | __GFP_ZERO, node); > } > > - > #ifdef CONFIG_NUMA > extern void *__kmalloc_node_track_caller(size_t size, gfp_t flags, int node, > unsigned long caller) __alloc_size(1); > -- > 2.25.1 > -- Thanks, Hyeonggon
