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x86/Kconfig: Further simplify the NR_CPUS config 

Clean up various aspects of the x86 CONFIG_NR_CPUS configuration switches:

- Rename the three CONFIG_NR_CPUS related variables to create a common
  namespace for them:

    RANGE_BEGIN_CPUS => NR_CPUS_RANGE_BEGIN
    RANGE_END_CPUS   => NR_CPUS_RANGE_END
    DEF_CONFIG_CPUS  => NR_CPUS_DEFAULT

- Align them vertically, such as:

    config NR_CPUS_RANGE_END
            int
            depends on X86_64
            default 8192 if  SMP && ( MAXSMP ||  CPUMASK_OFFSTACK)
            default  512 if  SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
            default    1 if !SMP

- Update help text, add more comments.

Test results:

 # i386 allnoconfig:
 CONFIG_NR_CPUS_RANGE_BEGIN=1
 CONFIG_NR_CPUS_RANGE_END=1
 CONFIG_NR_CPUS_DEFAULT=1
 CONFIG_NR_CPUS=1

 # i386 defconfig:
 CONFIG_NR_CPUS_RANGE_BEGIN=2
 CONFIG_NR_CPUS_RANGE_END=8
 CONFIG_NR_CPUS_DEFAULT=8
 CONFIG_NR_CPUS=8

 # i386 allyesconfig:
 CONFIG_NR_CPUS_RANGE_BEGIN=2
 CONFIG_NR_CPUS_RANGE_END=64
 CONFIG_NR_CPUS_DEFAULT=32
 CONFIG_NR_CPUS=32

 # x86_64 allnoconfig:
 CONFIG_NR_CPUS_RANGE_BEGIN=1
 CONFIG_NR_CPUS_RANGE_END=1
 CONFIG_NR_CPUS_DEFAULT=1
 CONFIG_NR_CPUS=1

 # x86_64 defconfig:
 CONFIG_NR_CPUS_RANGE_BEGIN=2
 CONFIG_NR_CPUS_RANGE_END=512
 CONFIG_NR_CPUS_DEFAULT=64
 CONFIG_NR_CPUS=64

 # x86_64 allyesconfig:
 CONFIG_NR_CPUS_RANGE_BEGIN=8192
 CONFIG_NR_CPUS_RANGE_END=8192
 CONFIG_NR_CPUS_DEFAULT=8192
 CONFIG_NR_CPUS=8192

Acked-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180210113629.jcv6su3r4suuno63@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2018-02-10 12:36:29 +01:00
parent a0d0bb4deb
commit aec6487e99
1 changed files with 40 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

66
arch/x86/Kconfig
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@ -949,52 +949,66 @@ config MAXSMP
Enable maximum number of CPUS and NUMA Nodes for this architecture.
If unsure, say N.
config RANGE_END_CPUS
#
# The maximum number of CPUs supported:
#
# The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
# and which can be configured interactively in the
# [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
#
# The ranges are different on 32-bit and 64-bit kernels, depending on
# hardware capabilities and scalability features of the kernel.
#
# ( If MAXSMP is enabled we just use the highest possible value and disable
# interactive configuration. )
#
config NR_CPUS_RANGE_BEGIN
int
default NR_CPUS_RANGE_END if MAXSMP
default 1 if !SMP
default 2
config NR_CPUS_RANGE_END
int
depends on X86_32
default 8 if SMP && !X86_BIGSMP
default 64 if SMP && X86_BIGSMP
default 1 if !SMP
default 64 if SMP && X86_BIGSMP
default 8 if SMP && !X86_BIGSMP
default 1 if !SMP
config RANGE_END_CPUS
config NR_CPUS_RANGE_END
int
depends on X86_64
default 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK
default 8192 if SMP && (MAXSMP || CPUMASK_OFFSTACK)
default 1 if !SMP
default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
default 1 if !SMP
config RANGE_BEGIN_CPUS
int
default 1 if !SMP
default RANGE_END_CPUS if MAXSMP
default 2
config DEF_CONFIG_CPUS
config NR_CPUS_DEFAULT
int
depends on X86_32
default 1 if !SMP
default 32 if X86_BIGSMP
default 8 if SMP
default 32 if X86_BIGSMP
default 8 if SMP
default 1 if !SMP
config DEF_CONFIG_CPUS
config NR_CPUS_DEFAULT
int
depends on X86_64
default 1 if !SMP
default 8192 if MAXSMP
default 64 if SMP
default 8192 if MAXSMP
default 64 if SMP
default 1 if !SMP
config NR_CPUS
int "Maximum number of CPUs" if SMP && !MAXSMP
range RANGE_BEGIN_CPUS RANGE_END_CPUS
default DEF_CONFIG_CPUS
range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
default NR_CPUS_DEFAULT
---help---
This allows you to specify the maximum number of CPUs which this
kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
supported value is 8192, otherwise the maximum value is 512. The
minimum value which makes sense is 2.
This is purely to save memory - each supported CPU adds
approximately eight kilobytes to the kernel image.
This is purely to save memory: each supported CPU adds about 8KB
to the kernel image.
config SCHED_SMT
bool "SMT (Hyperthreading) scheduler support"