linux-kernel - Re: [PATCH v2 0/8] Improve performance of VM translation on x86

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Date:	Fri, 12 Oct 2012 10:12:53 -0400
From:	Konrad Rzeszutek Wilk <konrad@...nel.org>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	andi@...stfloor.org, linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v2 0/8] Improve performance of VM translation on x86_64

On Thu, Oct 11, 2012 at 4:49 PM, Alexander Duyck
<alexander.h.duyck@...el.com> wrote:
> This patch series is meant to address several issues I encountered with VM
> translations on x86_64.  In my testing I found that swiotlb was incurring up
> to a 5% processing overhead due to calls to __phys_addr.  To address that I
> have updated swiotlb to use physical addresses instead of virtual addresses
> to reduce the need to call __phys_addr.  However those patches didn't address
> the other callers.  With these patches applied I am able to achieve an
> additional 1% to 2% performance gain on top of the changes to swiotlb.
>
> The first 2 patches are the performance optimizations that result in the 1% to
> 2% increase in overall performance.  The remaining patches are various
> cleanups for a number of spots where __pa or virt_to_phys was being called
> and was not needed or __pa_symbol could have been used.
>

Could you also add  a blurb in the Documentation/< appropriate file
for device driver writes> mentioning the usage of __pa_symbol is
preferred?

> ---
>
> Alexander Duyck (8):
>       x86/lguest: Use __pa_symbol instead of __pa on C visible symbols
>       x86/acpi: Use __pa_symbol instead of __pa on C visible symbols
>       x86/xen: Use __pa_symbol instead of __pa on C visible symbols
>       x86/ftrace: Use __pa_symbol instead of __pa on C visible symbols
>       x86: Use __pa_symbol instead of __pa on C visible symbols
>       x86: Drop 4 unnecessary calls to __pa_symbol
>       x86: Make it so that __pa_symbol can only process kernel symbols on x86_64
>       x86: Improve __phys_addr performance by making use of carry flags and inlining
>
>
>  arch/x86/include/asm/page.h          |    3 ++-
>  arch/x86/include/asm/page_32.h       |    1 +
>  arch/x86/include/asm/page_64_types.h |   20 +++++++++++++++++--
>  arch/x86/kernel/acpi/sleep.c         |    2 +-
>  arch/x86/kernel/cpu/intel.c          |    2 +-
>  arch/x86/kernel/ftrace.c             |    4 ++--
>  arch/x86/kernel/head32.c             |    4 ++--
>  arch/x86/kernel/head64.c             |    4 ++--
>  arch/x86/kernel/setup.c              |   16 ++++++++--------
>  arch/x86/kernel/x8664_ksyms_64.c     |    3 +++
>  arch/x86/lguest/boot.c               |    3 ++-
>  arch/x86/mm/pageattr.c               |    8 ++++----
>  arch/x86/mm/physaddr.c               |   35 ++++++++++++++++++++++++++++------
>  arch/x86/platform/efi/efi.c          |    4 ++--
>  arch/x86/realmode/init.c             |    8 ++++----
>  arch/x86/xen/mmu.c                   |   19 ++++++++++--------
>  16 files changed, 91 insertions(+), 45 deletions(-)
>
> --
> --
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