* NR_CPUS configuration option wrong
@ 2010-05-20 17:34 Frank A. Kingswood
2010-05-20 17:38 ` Randy Dunlap
0 siblings, 1 reply; 4+ messages in thread
From: Frank A. Kingswood @ 2010-05-20 17:34 UTC (permalink / raw)
To: linux-kernel
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
Frank
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: NR_CPUS configuration option wrong
2010-05-20 17:34 NR_CPUS configuration option wrong Frank A. Kingswood
@ 2010-05-20 17:38 ` Randy Dunlap
2010-05-20 18:32 ` Frank A. Kingswood
0 siblings, 1 reply; 4+ messages in thread
From: Randy Dunlap @ 2010-05-20 17:38 UTC (permalink / raw)
To: Frank A. Kingswood; +Cc: linux-kernel
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
OK?
---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: NR_CPUS configuration option wrong
2010-05-20 17:38 ` Randy Dunlap
@ 2010-05-20 18:32 ` Frank A. Kingswood
2010-05-20 18:35 ` Randy Dunlap
0 siblings, 1 reply; 4+ messages in thread
From: Frank A. Kingswood @ 2010-05-20 18:32 UTC (permalink / raw)
To: Randy Dunlap; +Cc: linux-kernel
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.
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.
Thanks,
Frank
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: NR_CPUS configuration option wrong
2010-05-20 18:32 ` Frank A. Kingswood
@ 2010-05-20 18:35 ` Randy Dunlap
0 siblings, 0 replies; 4+ messages in thread
From: Randy Dunlap @ 2010-05-20 18:35 UTC (permalink / raw)
To: Frank A. Kingswood; +Cc: linux-kernel
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 ***
^ permalink raw reply [flat|nested] 4+ messages in thread
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2010-05-20 17:34 NR_CPUS configuration option wrong Frank A. Kingswood
2010-05-20 17:38 ` Randy Dunlap
2010-05-20 18:32 ` Frank A. Kingswood
2010-05-20 18:35 ` Randy Dunlap
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