Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756878Ab2JISuo (ORCPT ); Tue, 9 Oct 2012 14:50:44 -0400 Received: from mga14.intel.com ([143.182.124.37]:10458 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751332Ab2JISul (ORCPT ); Tue, 9 Oct 2012 14:50:41 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.80,561,1344236400"; d="scan'208";a="202467002" From: Alexander Duyck Subject: [PATCH] x86: Improve 64 bit __phys_addr call performance To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, andi@firstfloor.org Cc: linux-kernel@vger.kernel.org, x86@kernel.org Date: Tue, 09 Oct 2012 11:50:58 -0700 Message-ID: <20121009185057.15478.86075.stgit@gitlad.jf.intel.com> User-Agent: StGIT/0.14.2 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4593 Lines: 130 This patch is meant to improve overall system performance when making use of the __phys_addr call on 64 bit x86 systems. To do this I have implemented several changes. First if CONFIG_DEBUG_VIRTUAL is not defined __phys_addr is made an inline, similar to how this is currently handled in 32 bit. However in order to do this it is required to export phys_base so that it is available if __phys_addr is used in kernel modules. The second change was to streamline the code by making use of the carry flag on an add operation instead of performing a compare on a 64 bit value. The advantage to this is that it allows us to reduce the overall size of the call. On my Xeon E5 system the entire __phys_addr inline call consumes 30 bytes and 5 instructions. I also applied similar logic to the debug version of the function. My testing shows that the debug version of the function with this patch applied is slightly faster than the non-debug version without the patch. Finally, when building the kernel with the first two changes applied I saw build warnings about __START_KERNEL_map and PAGE_OFFSET constants not fitting in their type. In order to resolve the build warning I changed their type from UL to ULL. Signed-off-by: Alexander Duyck --- arch/x86/include/asm/page_64_types.h | 16 ++++++++++++++-- arch/x86/kernel/x8664_ksyms_64.c | 3 +++ arch/x86/mm/physaddr.c | 20 ++++++++++++++------ 3 files changed, 31 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h index 320f7bb..a951e4d 100644 --- a/arch/x86/include/asm/page_64_types.h +++ b/arch/x86/include/asm/page_64_types.h @@ -30,14 +30,14 @@ * hypervisor to fit. Choosing 16 slots here is arbitrary, but it's * what Xen requires. */ -#define __PAGE_OFFSET _AC(0xffff880000000000, UL) +#define __PAGE_OFFSET _AC(0xffff880000000000, ULL) #define __PHYSICAL_START ((CONFIG_PHYSICAL_START + \ (CONFIG_PHYSICAL_ALIGN - 1)) & \ ~(CONFIG_PHYSICAL_ALIGN - 1)) #define __START_KERNEL (__START_KERNEL_map + __PHYSICAL_START) -#define __START_KERNEL_map _AC(0xffffffff80000000, UL) +#define __START_KERNEL_map _AC(0xffffffff80000000, ULL) /* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */ #define __PHYSICAL_MASK_SHIFT 46 @@ -58,7 +58,19 @@ void copy_page(void *to, void *from); extern unsigned long max_pfn; extern unsigned long phys_base; +#ifdef CONFIG_DEBUG_VIRTUAL extern unsigned long __phys_addr(unsigned long); +#else +static inline unsigned long __phys_addr(unsigned long x) +{ + unsigned long y = x - __START_KERNEL_map; + + /* use the carry flag to determine if x was < __START_KERNEL_map */ + x = y + ((x > y) ? phys_base : (__START_KERNEL_map - PAGE_OFFSET)); + + return x; +} +#endif #define __phys_reloc_hide(x) (x) #define vmemmap ((struct page *)VMEMMAP_START) diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c index 1330dd1..b014d94 100644 --- a/arch/x86/kernel/x8664_ksyms_64.c +++ b/arch/x86/kernel/x8664_ksyms_64.c @@ -59,6 +59,9 @@ EXPORT_SYMBOL(memcpy); EXPORT_SYMBOL(__memcpy); EXPORT_SYMBOL(memmove); +#ifndef CONFIG_DEBUG_VIRTUAL +EXPORT_SYMBOL(phys_base); +#endif EXPORT_SYMBOL(empty_zero_page); #ifndef CONFIG_PARAVIRT EXPORT_SYMBOL(native_load_gs_index); diff --git a/arch/x86/mm/physaddr.c b/arch/x86/mm/physaddr.c index d2e2735..f63bec5 100644 --- a/arch/x86/mm/physaddr.c +++ b/arch/x86/mm/physaddr.c @@ -8,20 +8,28 @@ #ifdef CONFIG_X86_64 +#ifdef CONFIG_DEBUG_VIRTUAL unsigned long __phys_addr(unsigned long x) { - if (x >= __START_KERNEL_map) { - x -= __START_KERNEL_map; - VIRTUAL_BUG_ON(x >= KERNEL_IMAGE_SIZE); - x += phys_base; + unsigned long y = x - __START_KERNEL_map; + + /* use the carry flag to determine if x was < __START_KERNEL_map */ + if (unlikely(x > y)) { + x = y + phys_base; + + VIRTUAL_BUG_ON(y >= KERNEL_IMAGE_SIZE); } else { - VIRTUAL_BUG_ON(x < PAGE_OFFSET); - x -= PAGE_OFFSET; + x = y + (__START_KERNEL_map - PAGE_OFFSET); + + /* carry flag will be set if starting x was >= PAGE_OFFSET */ + VIRTUAL_BUG_ON(x > y); VIRTUAL_BUG_ON(!phys_addr_valid(x)); } + return x; } EXPORT_SYMBOL(__phys_addr); +#endif bool __virt_addr_valid(unsigned long x) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/