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SubjectRe: [PATCH 2/2] x86: Modify Kconfig to allow up to 4096 cpus
Adrian Bunk wrote:
> On Wed, Mar 26, 2008 at 09:31:22AM -0700, Mike Travis wrote:
>> Adrian Bunk wrote:
>>> On Tue, Mar 25, 2008 at 06:41:39PM -0700, Mike Travis 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).
>>>
>>> I'm not really getting the point of MAXSMP - people should simply pick
>>> their values, and when they want the maximum "(2-4096)" and "(1-15)"
>>> already provide this information (except that your patch hides the
>>> latter information from the user).
>>>
>>> And with your patch, even with MAXSMP=y people could still set
>>> NR_CPUS=7 and NODES_SHIFT=15 or whatever else they want...
>>>
>>> More interesting would be why you want it to set NODES_SHIFT to
>>> something less than the maximum value of 15. I'm getting the fact that
>>> 2^15 > 4096 and that 15 might be nonsensical high, but this sounds more
>>> like requiring a patch to limit the range to 9?
>> I guess the main effect is that "MAXSMP" represents what's really
>> usable for an architecture based on other factors. The limit of
>> NODES_SHIFT = 15 is that it's represented in some places as a signed
>> 16-bit value, so 15 is the hard limit without coding changes, not
>> an architecture limit.
>
>
> This is the x86-specific Kconfig file that presents the x86 specific
> limits to the users.
>
> If NODES_SHIFT=15 is offered to the user although it's higher than the
> current architecture limit on x86 then this is simply a bug that should
> be fixed.
>
>
>> Thanks,
>> Mike
>
> cu
> Adrian
>

Ok, I'll modify it in the next version.

Thanks!
Mike


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