lkml.org 
[lkml]   [2018]   [Feb]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:x86/urgent] x86/Kconfig: Further simplify the NR_CPUS config
Commit-ID:  aec6487e994d2f625197970a56a4aac40c2c7547
Gitweb: https://git.kernel.org/tip/aec6487e994d2f625197970a56a4aac40c2c7547
Author: Ingo Molnar <mingo@kernel.org>
AuthorDate: Sat, 10 Feb 2018 12:36:29 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 11 Feb 2018 11:51:34 +0100

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>
---
arch/x86/Kconfig | 66 ++++++++++++++++++++++++++++++++++----------------------
1 file changed, 40 insertions(+), 26 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9d921b7..a528c14 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -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
- depends on X86_32
- default 8 if SMP && !X86_BIGSMP
- default 64 if SMP && X86_BIGSMP
- default 1 if !SMP
+ default NR_CPUS_RANGE_END if MAXSMP
+ default 1 if !SMP
+ default 2

-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
+ depends on X86_32
+ default 64 if SMP && X86_BIGSMP
+ default 8 if SMP && !X86_BIGSMP
+ default 1 if !SMP

-config RANGE_BEGIN_CPUS
+config NR_CPUS_RANGE_END
int
- default 1 if !SMP
- default RANGE_END_CPUS if MAXSMP
- default 2
+ depends on X86_64
+ default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
+ default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
+ default 1 if !SMP

-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"
\
 
 \ /
  Last update: 2018-02-12 02:21    [W:0.096 / U:0.456 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site