From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maksym Planeta Date: Sat, 19 Mar 2011 16:08:01 +0000 Subject: [PATCH] x86: page: get_order() optimization Message-Id: <1300550881-22091-1-git-send-email-mcsim.planeta@gmail.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: tglx@linutronix.de Cc: kernel-janitors@vger.kernel.org, mingo@redhat.com, linux-kernel@vger.kernel.org, Maksym Planeta 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 -#include #define __HAVE_ARCH_GATE_AREA 1 -- 1.7.2.3