linux-kernel - Re: NR_CPUS configuration option wrong

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Message-ID: <4BF580ED.3080207@oracle.com>
Date:	Thu, 20 May 2010 11:35:25 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	"Frank A. Kingswood" <frank@...gswood-consulting.co.uk>
CC:	linux-kernel@...r.kernel.org
Subject: Re: NR_CPUS configuration option wrong

On 05/20/10 11:32, Frank A. Kingswood wrote:
> Randy Dunlap wrote:
>> On Thu, 20 May 2010 18:34:32 +0100 Frank A. Kingswood wrote:
>>
>>> Hi!
>>>
>>> The configuration MAXSMP help text indicates it is used to enable
>>> configuration of number of CPUs. However, NR_CPUS depends on !MAXSMP.
>>>
>>> arch/x86/Kconfig:
>>> 758 config NR_CPUS
>>> 759         int "Maximum number of CPUs" if SMP && !MAXSMP
>>
>> That line depends on !MAXSMP.  Then below there, we find:
>>
>>     default "4096" if MAXSMP
> 
> Hah, weird.
> I can see now it is possible to parse the MAXSMP help this way, but it
> was not obvious.

Ambiguity is fairly easy.  :(

> In menuconfig you see two questions:
> 
> [ ] Configure Maximum number of SMP Processors and NUMA Nodes
> [8] Maximum number of CPUs
> 
> and setting the first one YES makes the second one go away.
> 
> Perhaps restating the help as "Set number of SMP processors and NUMA
> nodes to the maximum that the kernel supports" might help.

Yes, that sounds better.  Want to submit a patch for that?

-- 
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
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