Messages in this thread | | | Date | Tue, 6 Nov 2012 00:08:03 +0200 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH v3 1/8] x86: Improve __phys_addr performance by making use of carry flags and inlining |
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On Mon, Nov 05, 2012 at 01:56:28PM -0800, Alexander Duyck wrote: > 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.
Realmode code compiles with -m32. I guess it's just wrong that it tries to include <asm/page_64_types.h>.
-- Kirill A. Shutemov
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