Commit bb61ccc7 authored Nov 05, 2013 by Josh Boyer Committed by Ingo Molnar Nov 06, 2013

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>

parent a477c859

arch/x86/Kconfig

+4 −2

Original line number	Diff line number	Diff line
		@@ -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