linux-kernel - Re: [patch] x86: enable GBPAGES option by default

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Date:	Wed, 22 Oct 2008 12:35:12 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [patch] x86: enable GBPAGES option by default

Oops, messed up Andi's email...

On Wed, Oct 22, 2008 at 12:33:16PM +0200, Nick Piggin wrote:
> DIRECT_GBPAGES was under DEBUG_KERNEL && EXPERIMENTAL and disabled by default.
> Turn it on by default and put it under EMBEDDED.
> 
> Signed-off-by: Nick Piggin <npiggin@...e.de>
> ---
> Index: linux-2.6/arch/x86/Kconfig
> ===================================================================
> --- linux-2.6.orig/arch/x86/Kconfig
> +++ linux-2.6/arch/x86/Kconfig
> @@ -946,6 +946,15 @@ config X86_PAE
>  config ARCH_PHYS_ADDR_T_64BIT
>         def_bool X86_64 || X86_PAE
>  
> +config DIRECT_GBPAGES
> +	bool "Enable 1GB pages for kernel pagetables" if EMBEDDED
> +	default y
> +	depends on X86_64
> +	help
> +	  Allow the kernel linear mapping to use 1GB pages on CPUs that
> +	  support it. This can improve the kernel's performance a tiny bit by
> +	  reducing TLB pressure. If in doubt, say "Y".
> +
>  # Common NUMA Features
>  config NUMA
>  	bool "Numa Memory Allocation and Scheduler Support (EXPERIMENTAL)"
> Index: linux-2.6/arch/x86/Kconfig.debug
> ===================================================================
> --- linux-2.6.orig/arch/x86/Kconfig.debug
> +++ linux-2.6/arch/x86/Kconfig.debug
> @@ -114,18 +114,6 @@ config DEBUG_RODATA
>  	  data. This is recommended so that we can catch kernel bugs sooner.
>  	  If in doubt, say "Y".
>  
> -config DIRECT_GBPAGES
> -	bool "Enable gbpages-mapped kernel pagetables"
> -	depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64
> -	help
> -	  Enable gigabyte pages support (if the CPU supports it). This can
> -	  improve the kernel's performance a tiny bit by reducing TLB
> -	  pressure.
> -
> -	  This is experimental code.
> -
> -	  If in doubt, say "N".
> -
>  config DEBUG_RODATA_TEST
>  	bool "Testcase for the DEBUG_RODATA feature"
>  	depends on DEBUG_RODATA
--
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