kernel: tweak the maximum allocation size to improve memory allocator performance

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@15130 3c298f89-4303-0410-b956-a3cf2f4a3e73

target/linux/generic-2.6/patches-2.6.28/203-slab_maxsize.patch

+--- a/include/linux/slab.h
++++ b/include/linux/slab.h
+@@ -115,8 +115,8 @@ int kmem_ptr_validate(struct kmem_cache 
+  * to do various tricks to work around compiler limitations in order to
+  * ensure proper constant folding.
+  */
+-#define KMALLOC_SHIFT_HIGH	((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
+-				(MAX_ORDER + PAGE_SHIFT - 1) : 25)
++#define KMALLOC_SHIFT_HIGH	((MAX_ORDER + PAGE_SHIFT - 1) <= 17 ? \
++				(MAX_ORDER + PAGE_SHIFT - 1) : 17)
+ 
+ #define KMALLOC_MAX_SIZE	(1UL << KMALLOC_SHIFT_HIGH)
+ #define KMALLOC_MAX_ORDER	(KMALLOC_SHIFT_HIGH - PAGE_SHIFT)