From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756675Ab1CSQGN (ORCPT ); Sat, 19 Mar 2011 12:06:13 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:48282 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755277Ab1CSQGJ (ORCPT ); Sat, 19 Mar 2011 12:06:09 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer; b=YVAIHwjlZp0ESvBbbQMbGnTJ5uesB0WbgNP5mLqUYnj31GBJmMZ3GH85/hi7OuYep/ yHxO7us6A7A0Bta76Ltjq+NZuUtur5tu6nxqMadHEGTQJd0pMhMjodvPQgfM/P+TLU2E LFWtmucBjhmtIAsOYDYq/LqkHuAM/fDVAyvY0= From: Maksym Planeta To: tglx@linutronix.de Cc: kernel-janitors@vger.kernel.org, mingo@redhat.com, linux-kernel@vger.kernel.org, Maksym Planeta Subject: [PATCH] x86: page: get_order() optimization Date: Sat, 19 Mar 2011 18:08:01 +0200 Message-Id: <1300550881-22091-1-git-send-email-mcsim.planeta@gmail.com> X-Mailer: git-send-email 1.7.2.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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