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x86/cpu: Allow higher NR_CPUS values 

The current range for SMP configs is 2 - 512 CPUs, or a full
4096 in the case of MAXSMP.  There are machines that have 1024
CPUs in them today and configuring a kernel for that means you
are forced to set MAXSMP.  This adds additional unnecessary
overhead.  While that overhead might be considered tiny for
large machines, it isn't necessarily so if you are building a
kernel that runs across a wide variety of machines.

To cover the range of more common machines today, we allow
NR_CPUS to be up to 4096 when CPUMASK_OFFSTACK is enabled.

Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Cc: prarit@redhat.com
Cc: Russ Anderson <rja@sgi.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20131105143728.GJ9944@hansolo.jdub.homelinux.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Boyer 2013-11-05 09:37:29 -05:00 committed by Ingo Molnar
parent a477c8594b
commit bb61ccc7db
1 changed files with 4 additions and 2 deletions
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6
arch/x86/Kconfig
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@ -825,14 +825,16 @@ config MAXSMP
config NR_CPUS
int "Maximum number of CPUs" if SMP && !MAXSMP
range 2 8 if SMP && X86_32 && !X86_BIGSMP
range 2 512 if SMP && !MAXSMP
range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK
range 2 4096 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
default "1" if !SMP
default "4096" if MAXSMP
default "32" if SMP && (X86_NUMAQ || X86_SUMMIT || X86_BIGSMP || X86_ES7000)
default "8" if SMP
---help---
This allows you to specify the maximum number of CPUs which this
kernel will support. The maximum supported value is 512 and the
kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
supported value is 4096, otherwise the maximum value is 512. The
minimum value which makes sense is 2.
This is purely to save memory - each supported CPU adds