[PATCH] x86: page: get_order() optimization
From: Maksym Planeta <hidden>
Date: 2011-03-19 16:06:13
Also in:
lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
For x86 architecture get_order function can be optimized due to assembler instruction bsr. --- arch/x86/include/asm/page.h | 20 +++++++++++++++++++- 1 files changed, 19 insertions(+), 1 deletions(-)
diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
index 8ca8283..339ae26 100644
--- a/arch/x86/include/asm/page.h
+++ b/arch/x86/include/asm/page.h@@ -60,10 +60,28 @@ static inline void copy_user_page(void *to, void *from, unsigned long vaddr, extern bool __virt_addr_valid(unsigned long kaddr); #define virt_addr_valid(kaddr) __virt_addr_valid((unsigned long) (kaddr)) +/* Pure 2^n version of get_order */ +static inline __attribute_const__ int get_order(unsigned long size) +{ + int order; + + size = (size - 1) >> (PAGE_SHIFT - 1); +#ifdef CONFIG_X86_CMOV + asm("bsr %1,%0\n\t" + "cmovzl %2,%0" + : "=&r" (order) : "rm" (size), "rm" (0)); +#else + asm("bsr %1,%0\n\t" + "jnz 1f\n\t" + "movl $0,%0\n" + "1:" : "=r" (order) : "rm" (size)); +#endif + return order; +} + #endif /* __ASSEMBLY__ */ #include <asm-generic/memory_model.h> -#include <asm-generic/getorder.h> #define __HAVE_ARCH_GATE_AREA 1
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1.7.2.3