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Date: Mon, 05 Nov 2012 13:56:28 -0800 From: Alexander Duyck <alexander.h.duyck@...el.com> To: "Kirill A. Shutemov" <kirill@...temov.name> CC: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, andi@...stfloor.org, linux-kernel@...r.kernel.org, x86@...nel.org Subject: Re: [PATCH v3 1/8] x86: Improve __phys_addr performance by making use of carry flags and inlining On 11/05/2012 12:24 PM, Kirill A. Shutemov wrote: > On Mon, Nov 05, 2012 at 11:04:06AM -0800, Alexander Duyck wrote: >> This patch is meant to improve overall system performance when making use of >> the __phys_addr call. 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 significantly reduce the overall >> size of the call. On my Xeon E5 system the entire __phys_addr inline call >> consumes a little less than 32 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. >> >> 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. > What kind of warning messages did you see? > It's strange: sizeof(unsinged long) == sizeof(unsinged long long) on > x86_64 One of the warnings is included below: In file included from /usr/src/kernels/linux-next/arch/x86/include/asm/page_types.h:37, from /usr/src/kernels/linux-next/arch/x86/include/asm/pgtable_types.h:5, from /usr/src/kernels/linux-next/arch/x86/include/asm/boot.h:11, from arch/x86/realmode/rm/../../boot/boot.h:26, from arch/x86/realmode/rm/../../boot/regs.c:19, from arch/x86/realmode/rm/regs.c:1: /usr/src/kernels/linux-next/arch/x86/include/asm/page_64_types.h: In function '__phys_addr_nodebug': /usr/src/kernels/linux-next/arch/x86/include/asm/page_64_types.h:63: warning: integer constant is too large for 'unsigned long' type /usr/src/kernels/linux-next/arch/x86/include/asm/page_64_types.h:66: warning: integer constant is too large for 'unsigned long' type /usr/src/kernels/linux-next/arch/x86/include/asm/page_64_types.h:66: warning: integer constant is too large for 'unsigned long' type The warnings all seemed to originate from several different spots throughout the x86 tree. All of the warning messages include arch/x86/boot/boot.h:26 and then from there up the included from list is always the same. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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