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;
+
+ if (size <= 8)
+ return 3;
+
+ /* Following compile-time optimization rule is mandatory. */
+ if (size <= 32 * 1024 * 1024)
+ return order_base_2(size);
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
