linux-kernel - Re: [PATCH 2/2] x86: Modify Kconfig to allow up to 4096 cpus

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Date:	Wed, 26 Mar 2008 12:28:28 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Mike Travis" <travis@....com>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...e.hu>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86: Modify Kconfig to allow up to 4096 cpus

On Tue, Mar 25, 2008 at 6:41 PM, Mike Travis <travis@....com> wrote:
> Increase the limit of NR_CPUS to 4096 and introduce a boolean
>  called "MAXSMP" which when set (e.g. "allyesconfig"), will set
>  NR_CPUS = 4096 and NODES_SHIFT = 9 (512).
>
>  Based on:
>         git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
>         git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-x86.git
>
>  Signed-off-by: Mike Travis <travis@....com>
>  ---
>   arch/x86/Kconfig |   20 ++++++++++++++++----
>   1 file changed, 16 insertions(+), 4 deletions(-)
>
>  --- linux.trees.git.orig/arch/x86/Kconfig
>  +++ linux.trees.git/arch/x86/Kconfig
>  @@ -522,16 +522,24 @@ config SWIOTLB
>           access 32-bits of memory can be used on systems with more than
>           3 GB of memory. If unsure, say Y.
>
>  +config MAXSMP
>  +       bool "Configure Maximum number of SMP Processors"
>  +       depends on X86_64 && SMP
>  +       default n
>  +       help
>  +         Configure maximum number of CPUS for this architecture.
>  +         If unsure, say N.
>
>   config NR_CPUS
>  -       int "Maximum number of CPUs (2-255)"
>  -       range 2 255
>  +       int "Maximum number of CPUs (2-4096)"
>  +       range 2 4096
>         depends on SMP
>  +       default "4096" if MAXSMP
>         default "32" if X86_NUMAQ || X86_SUMMIT || X86_BIGSMP || X86_ES7000
>         default "8"
>         help
>           This allows you to specify the maximum number of CPUs which this
>  -         kernel will support.  The maximum supported value is 255 and the
>  +         kernel will support.  The maximum supported value is 4096 and the
>           minimum value which makes sense is 2.
>
>           This is purely to save memory - each supported CPU adds

or put
if  MAXSMP around NR_CPUS...

YH
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