Dave,
Attached patch is a lovely rendition of the CONFIG_NR_CPUS patch Andrew
and I have been tossing around.
The patch allows the user to set a sane value for NR_CPUS at
compile-time if building an SMP kernel. The benefits are saved cycles
and memory/object size reduction.
Further, this patch defines a per-arch default value for NR_CPUS thus
64-bit architectures can support a value of 64 instead of the current
global 32.
The patch is tested on i386 with various values for NR_CPUS. Other
32-bit architectures will be fine with the default but may need minor
fixing of poor assumptions to boot with other values. 64-bit
architectures may need further fixing as I defaulted them to 64.
Patch is against 2.5.23-dj2. Enjoy,
Robert Love
diff -urN linux-2.5.23-dj2/arch/alpha/config.in linux/arch/alpha/config.in
--- linux-2.5.23-dj2/arch/alpha/config.in Wed Jun 19 17:31:21 2002
+++ linux/arch/alpha/config.in Wed Jun 19 17:26:35 2002
@@ -232,6 +232,7 @@
if [ "$CONFIG_SMP" = "y" ]; then
define_bool CONFIG_HAVE_DEC_LOCK y
+ int 'Maximum number of CPUs (2-64)' CONFIG_NR_CPUS 64
fi
if [ "$CONFIG_EXPERIMENTAL" = "y" ]; then
diff -urN linux-2.5.23-dj2/arch/i386/Config.help linux/arch/i386/Config.help
--- linux-2.5.23-dj2/arch/i386/Config.help Wed Jun 19 17:32:33 2002
+++ linux/arch/i386/Config.help Wed Jun 19 17:26:35 2002
@@ -25,6 +25,14 @@
If you don't know what to do here, say N.
+CONFIG_NR_CPUS
+ This allows you to specify the maximum number of CPUs which this
+ kernel will support. The maximum supported value is 32 and 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.
+
CONFIG_PREEMPT
This option reduces the latency of the kernel when reacting to
real-time or interactive events by allowing a low priority process to
diff -urN linux-2.5.23-dj2/arch/i386/config.in linux/arch/i386/config.in
--- linux-2.5.23-dj2/arch/i386/config.in Wed Jun 19 17:32:33 2002
+++ linux/arch/i386/config.in Wed Jun 19 17:26:35 2002
@@ -164,6 +164,7 @@
define_bool CONFIG_X86_IO_APIC y
fi
else
+ int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32
bool 'Multiquad NUMA system' CONFIG_MULTIQUAD
fi
diff -urN linux-2.5.23-dj2/arch/i386/defconfig linux/arch/i386/defconfig
--- linux-2.5.23-dj2/arch/i386/defconfig Wed Jun 19 17:32:33 2002
+++ linux/arch/i386/defconfig Wed Jun 19 17:26:35 2002
@@ -74,6 +74,7 @@
# CONFIG_PREEMPT is not set
# CONFIG_MULTIQUAD is not set
CONFIG_HAVE_DEC_LOCK=y
+CONFIG_NR_CPUS=32
#
# General options
diff -urN linux-2.5.23-dj2/arch/ia64/config.in linux/arch/ia64/config.in
--- linux-2.5.23-dj2/arch/ia64/config.in Wed Jun 19 17:32:34 2002
+++ linux/arch/ia64/config.in Wed Jun 19 17:26:35 2002
@@ -95,6 +95,10 @@
tristate '/proc/pal support' CONFIG_IA64_PALINFO
tristate '/proc/efi/vars support' CONFIG_EFI_VARS
+if [ "$CONFIG_SMP" = "y" ]; then
+ int 'Maximum number of CPUs (2-64)' CONFIG_NR_CPUS 64
+fi
+
tristate 'Kernel support for ELF binaries' CONFIG_BINFMT_ELF
tristate 'Kernel support for MISC binaries' CONFIG_BINFMT_MISC
diff -urN linux-2.5.23-dj2/arch/ia64/defconfig linux/arch/ia64/defconfig
--- linux-2.5.23-dj2/arch/ia64/defconfig Wed Jun 19 17:31:23 2002
+++ linux/arch/ia64/defconfig Wed Jun 19 17:26:35 2002
@@ -61,6 +61,7 @@
CONFIG_EFI_VARS=y
CONFIG_BINFMT_ELF=y
# CONFIG_BINFMT_MISC is not set
+CONFIG_NR_CPUS=64
#
# ACPI Support
diff -urN linux-2.5.23-dj2/arch/mips/config.in linux/arch/mips/config.in
--- linux-2.5.23-dj2/arch/mips/config.in Wed Jun 19 17:32:34 2002
+++ linux/arch/mips/config.in Wed Jun 19 17:26:35 2002
@@ -501,6 +501,8 @@
bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ
if [ "$CONFIG_SMP" != "y" ]; then
bool 'Run uncached' CONFIG_MIPS_UNCACHED
+else
+ int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32
fi
endmenu
diff -urN linux-2.5.23-dj2/arch/mips64/config.in linux/arch/mips64/config.in
--- linux-2.5.23-dj2/arch/mips64/config.in Wed Jun 19 17:32:34 2002
+++ linux/arch/mips64/config.in Wed Jun 19 17:26:35 2002
@@ -248,6 +248,8 @@
bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ
if [ "$CONFIG_SMP" != "y" ]; then
bool 'Run uncached' CONFIG_MIPS_UNCACHED
+else
+ int 'Maximum number of CPUs (2-64)' CONFIG_NR_CPUS 64
fi
endmenu
diff -urN linux-2.5.23-dj2/arch/mips64/defconfig linux/arch/mips64/defconfig
--- linux-2.5.23-dj2/arch/mips64/defconfig Wed Jun 19 17:31:25 2002
+++ linux/arch/mips64/defconfig Wed Jun 19 17:26:35 2002
@@ -32,6 +32,7 @@
# CONFIG_EISA is not set
# CONFIG_MCA is not set
# CONFIG_SBUS is not set
+CONFIG_NR_CPUS=64
#
# CPU selection
diff -urN linux-2.5.23-dj2/arch/parisc/config.in linux/arch/parisc/config.in
--- linux-2.5.23-dj2/arch/parisc/config.in Wed Jun 19 17:32:34 2002
+++ linux/arch/parisc/config.in Wed Jun 19 17:26:35 2002
@@ -18,6 +18,10 @@
# bool 'Symmetric multi-processing support' CONFIG_SMP
define_bool CONFIG_SMP n
+if [ "$CONFIG_SMP" = "y" ]; then
+ int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32
+fi
+
bool 'Kernel Debugger support' CONFIG_KWDB
# define_bool CONFIG_KWDB n
diff -urN linux-2.5.23-dj2/arch/ppc/config.in linux/arch/ppc/config.in
--- linux-2.5.23-dj2/arch/ppc/config.in Wed Jun 19 17:31:16 2002
+++ linux/arch/ppc/config.in Wed Jun 19 17:26:35 2002
@@ -172,6 +172,7 @@
bool 'Symmetric multi-processing support' CONFIG_SMP
if [ "$CONFIG_SMP" = "y" ]; then
bool ' Distribute interrupts on all CPUs by default' CONFIG_IRQ_ALL_CPUS
+ int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32
fi
if [ "$CONFIG_SMP" != "y" ]; then
bool 'Preemptible Kernel' CONFIG_PREEMPT
diff -urN linux-2.5.23-dj2/arch/ppc64/config.in linux/arch/ppc64/config.in
--- linux-2.5.23-dj2/arch/ppc64/config.in Wed Jun 19 17:31:23 2002
+++ linux/arch/ppc64/config.in Wed Jun 19 17:26:35 2002
@@ -21,6 +21,7 @@
bool 'Symmetric multi-processing support' CONFIG_SMP
if [ "$CONFIG_SMP" = "y" ]; then
bool ' Distribute interrupts on all CPUs by default' CONFIG_IRQ_ALL_CPUS
+ int 'Maximum number of CPUs (2-64)' CONFIG_NR_CPUS 64
if [ "$CONFIG_PPC_PSERIES" = "y" ]; then
bool ' Hardware multithreading' CONFIG_HMT
fi
diff -urN linux-2.5.23-dj2/arch/ppc64/defconfig linux/arch/ppc64/defconfig
--- linux-2.5.23-dj2/arch/ppc64/defconfig Wed Jun 19 17:31:23 2002
+++ linux/arch/ppc64/defconfig Wed Jun 19 17:26:35 2002
@@ -38,6 +38,7 @@
CONFIG_IRQ_ALL_CPUS=y
# CONFIG_HMT is not set
# CONFIG_PREEMPT is not set
+CONFIG_NR_CPUS=64
#
# General setup
diff -urN linux-2.5.23-dj2/arch/s390/config.in linux/arch/s390/config.in
--- linux-2.5.23-dj2/arch/s390/config.in Wed Jun 19 17:31:26 2002
+++ linux/arch/s390/config.in Wed Jun 19 17:26:35 2002
@@ -20,6 +20,9 @@
comment 'Processor type and features'
bool 'Symmetric multi-processing support' CONFIG_SMP
bool 'IEEE FPU emulation' CONFIG_MATHEMU
+if [ "$CONFIG_SMP" = "y" ]; then
+ int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32
+fi
endmenu
mainmenu_option next_comment
diff -urN linux-2.5.23-dj2/arch/s390/defconfig linux/arch/s390/defconfig
--- linux-2.5.23-dj2/arch/s390/defconfig Wed Jun 19 17:31:26 2002
+++ linux/arch/s390/defconfig Wed Jun 19 17:26:35 2002
@@ -35,6 +35,7 @@
#
CONFIG_SMP=y
CONFIG_MATHEMU=y
+CONFIG_NR_CPUS=64
#
# Base setup
diff -urN linux-2.5.23-dj2/arch/s390x/config.in linux/arch/s390x/config.in
--- linux-2.5.23-dj2/arch/s390x/config.in Wed Jun 19 17:31:25 2002
+++ linux/arch/s390x/config.in Wed Jun 19 17:26:35 2002
@@ -19,6 +19,9 @@
mainmenu_option next_comment
comment 'Processor type and features'
bool 'Symmetric multi-processing support' CONFIG_SMP
+if [ "$CONFIG_SMP" = "y" ]; then
+ int 'Maximum number of CPUs (2-64)' CONFIG_NR_CPUS 64
+fi
bool 'Kernel support for 31 bit emulation' CONFIG_S390_SUPPORT
if [ "$CONFIG_S390_SUPPORT" = "y" ]; then
tristate 'Kernel support for 31 bit ELF binaries' CONFIG_BINFMT_ELF32
diff -urN linux-2.5.23-dj2/arch/s390x/defconfig linux/arch/s390x/defconfig
--- linux-2.5.23-dj2/arch/s390x/defconfig Wed Jun 19 17:31:25 2002
+++ linux/arch/s390x/defconfig Wed Jun 19 17:26:35 2002
@@ -36,6 +36,7 @@
CONFIG_SMP=y
CONFIG_S390_SUPPORT=y
CONFIG_BINFMT_ELF32=y
+CONFIG_NR_CPUS=64
#
# Base setup
diff -urN linux-2.5.23-dj2/arch/sparc/config.in linux/arch/sparc/config.in
--- linux-2.5.23-dj2/arch/sparc/config.in Wed Jun 19 17:31:21 2002
+++ linux/arch/sparc/config.in Wed Jun 19 17:26:35 2002
@@ -17,6 +17,10 @@
bool 'Symmetric multi-processing support (does not work on sun4/sun4c)' CONFIG_SMP
+if [ "$CONFIG_SMP" = "y" ]; then
+ int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32
+fi
+
# Identify this as a Sparc32 build
define_bool CONFIG_SPARC32 y
diff -urN linux-2.5.23-dj2/arch/sparc64/config.in linux/arch/sparc64/config.in
--- linux-2.5.23-dj2/arch/sparc64/config.in Wed Jun 19 17:32:35 2002
+++ linux/arch/sparc64/config.in Wed Jun 19 17:26:35 2002
@@ -17,6 +17,10 @@
bool 'Symmetric multi-processing support' CONFIG_SMP
bool 'Preemptible kernel' CONFIG_PREEMPT
+if [ "$CONFIG_SMP" = "y" ]; then
+ int 'Maximum number of CPUs (2-64)' CONFIG_NR_CPUS 64
+fi
+
# Identify this as a Sparc64 build
define_bool CONFIG_SPARC64 y
diff -urN linux-2.5.23-dj2/arch/sparc64/defconfig linux/arch/sparc64/defconfig
--- linux-2.5.23-dj2/arch/sparc64/defconfig Wed Jun 19 17:32:35 2002
+++ linux/arch/sparc64/defconfig Wed Jun 19 17:26:35 2002
@@ -63,6 +63,7 @@
CONFIG_BINFMT_MISC=m
# CONFIG_SUNOS_EMUL is not set
CONFIG_SOLARIS_EMUL=m
+CONFIG_NR_CPUS=64
#
# Parallel port support
diff -urN linux-2.5.23-dj2/arch/x86_64/config.in linux/arch/x86_64/config.in
--- linux-2.5.23-dj2/arch/x86_64/config.in Wed Jun 19 17:31:25 2002
+++ linux/arch/x86_64/config.in Wed Jun 19 17:29:25 2002
@@ -54,6 +54,7 @@
fi
if [ "$CONFIG_SMP" = "y" ]; then
define_bool CONFIG_HAVE_DEC_LOCK y
+ int 'Maximum number of CPUs (2-64)' CONFIG_NR_CPUS 64
fi
define_bool CONFIG_X86_MCE y
diff -urN linux-2.5.23-dj2/arch/x86_64/defconfig linux/arch/x86_64/defconfig
--- linux-2.5.23-dj2/arch/x86_64/defconfig Wed Jun 19 17:31:25 2002
+++ linux/arch/x86_64/defconfig Wed Jun 19 17:26:35 2002
@@ -51,6 +51,7 @@
CONFIG_HAVE_DEC_LOCK=y
CONFIG_X86_MCE=y
# CONFIG_X86_MCE_NONFATAL is not set
+CONFIG_NR_CPUS=64
#
# Power management options
diff -urN linux-2.5.23-dj2/include/linux/threads.h linux/include/linux/threads.h
--- linux-2.5.23-dj2/include/linux/threads.h Wed Jun 19 17:31:07 2002
+++ linux/include/linux/threads.h Wed Jun 19 17:26:35 2002
@@ -8,10 +8,16 @@
* /proc/sys/kernel/threads-max.
*/
+/*
+ * Maximum supported processors that can run under SMP. This value is
+ * set via configure setting. The maximum is equal to the size of the
+ * bitmasks used on that platform, i.e. 32 or 64. Setting this smaller
+ * saves quite a bit of memory.
+ */
#ifdef CONFIG_SMP
-#define NR_CPUS 32 /* Max processors that can be running in SMP */
+#define NR_CPUS CONFIG_NR_CPUS
#else
-#define NR_CPUS 1
+#define NR_CPUS 1
#endif
#define MIN_THREADS_LEFT_FOR_ROOT 4
On 2002.06.20 Robert Love wrote:
>Dave,
>
>Attached patch is a lovely rendition of the CONFIG_NR_CPUS patch Andrew
>and I have been tossing around.
>
Default for alpha is missing ?
--
J.A. Magallon \ Software is like sex: It's better when it's free
mailto:[email protected] \ -- Linus Torvalds, FSF T-shirt
Linux werewolf 2.4.19-pre10-jam3, Mandrake Linux 8.3 (Cooker) for i586
gcc (GCC) 3.1.1 (Mandrake Linux 8.3 3.1.1-0.4mdk)
On Thu, 2002-06-20 at 09:00, J.A. Magallon wrote:
> On 2002.06.20 Robert Love wrote:
>
> >Attached patch is a lovely rendition of the CONFIG_NR_CPUS patch Andrew
> >and I have been tossing around.
> >
>
> Default for alpha is missing ?
No... the default in 64 in config.in. Do you mean there is no defconfig
entry? Well that is because CONFIG_SMP is not set and CONFIG_NR_CPUS is
dependent on it.
Robert Love
On 2002.06.20 Robert Love wrote:
>On Thu, 2002-06-20 at 09:00, J.A. Magallon wrote:
>
>> On 2002.06.20 Robert Love wrote:
>>
>> >Attached patch is a lovely rendition of the CONFIG_NR_CPUS patch Andrew
>> >and I have been tossing around.
>> >
>>
>> Default for alpha is missing ?
>
>No... the default in 64 in config.in. Do you mean there is no defconfig
>entry? Well that is because CONFIG_SMP is not set and CONFIG_NR_CPUS is
>dependent on it.
>
Ok.
--
J.A. Magallon \ Software is like sex: It's better when it's free
mailto:[email protected] \ -- Linus Torvalds, FSF T-shirt
Linux werewolf 2.4.19-pre10-jam3, Mandrake Linux 8.3 (Cooker) for i586
gcc (GCC) 3.1.1 (Mandrake Linux 8.3 3.1.1-0.4mdk)