Linux-Kernel Archive: [PATCH] CONFIG_NR_CPUS, redux [PATCH] CONFIG_NR_CPUS, redux From: Robert Love (rml@tech9.net) Date: Tue Jun 11 2002 - 12:52:16 EST Next message: Oliver Neukum: "Re: PCI DMA to small buffers on cache-incoherent arch" Previous message: Ingo Molnar: "[patch] current scheduler bits #2, 2.5.21" Next in thread: Randy.Dunlap: "Re: [PATCH] CONFIG_NR_CPUS, redux" Reply: Randy.Dunlap: "Re: [PATCH] CONFIG_NR_CPUS, redux" Reply: Rob Radez: "Re: [PATCH] CONFIG_NR_CPUS, redux" Maybe reply: Matt_Domsch@Dell.com: "RE: [PATCH] CONFIG_NR_CPUS, redux" Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] On Tue, 2002-06-11 at 02:27, Andrew Morton wrote: > In which case, CONFIG_NR_CPUS is the only way to get the memory > back... Alright, so here we go. Andrew introduced this idea last week and here is a revised, perhaps final, version. We have two goals: (a) allow NR_CPUS to be set at configure time, to save on memory and gain an unmeasurable boost in speed (b) let each architecture define a default NR_CPUS, i.e. 64-bit architectures can have an NR_CPUS of 64 We do this fairly easily. In include/linux/threads.h: #ifdef CONFIG_SMP #define NR_CPUS CONFIG_NR_CPUS #else #define NR_CPUS 1 #endif and in each arch/xxx/config.in add a configure entry, conditional on CONFIG_SMP, for CONFIG_NR_CPUS with a proper default. If CONFIG_SMP is set in defconfig, set CONFIG_NR_CPUS properly there, too. Here are the defaults I picked: CONFIG_NR_CPUS=32: i386, mips, parisc, ppc, sparc CONFIG_NR_CPUS=64: alpha, ia64, mips64, ppc64, s390, s390x, sparc64, x86-64 No CONFIG_NR_CPUS: arm, cris, sh Andrew has pointed out some architectures may need minor tweaks to work with NR_CPUS < 32. He discovered and fixed a minor issue on i386... other architectures, please verify non-standard options work. Also make sure 64 works! Patch is against 2.5.21, enjoy... Robert Love diff -urN linux-2.5.21/arch/alpha/config.in linux/arch/alpha/config.in --- linux-2.5.21/arch/alpha/config.in Sat Jun 8 22:28:07 2002 +++ linux/arch/alpha/config.in Sun Jun 9 13:22:46 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-2.5.21/arch/i386/Config.help linux/arch/i386/Config.help --- linux-2.5.21/arch/i386/Config.help Sat Jun 8 22:27:21 2002 +++ linux/arch/i386/Config.help Sun Jun 9 13:13:02 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 + mimimum 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-2.5.21/arch/i386/config.in linux/arch/i386/config.in --- linux-2.5.21/arch/i386/config.in Sat Jun 8 22:28:47 2002 +++ linux/arch/i386/config.in Sun Jun 9 13:23:20 2002 @@ -185,8 +185,8 @@ bool 'Math emulation' CONFIG_MATH_EMULATION bool 'MTRR (Memory Type Range Register) support' CONFIG_MTRR -bool 'Symmetric multi-processing support' CONFIG_SMP bool 'Preemptible Kernel' CONFIG_PREEMPT +bool 'Symmetric multi-processing support' CONFIG_SMP if [ "$CONFIG_SMP" != "y" ]; then bool 'Local APIC support on uniprocessors' CONFIG_X86_UP_APIC dep_bool 'IO-APIC support on uniprocessors' CONFIG_X86_UP_IOAPIC $CONFIG_X86_UP_APIC @@ -197,6 +197,7 @@ define_bool CONFIG_X86_IO_APIC y fi else + int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32 bool 'Multiquad NUMA system' CONFIG_MULTIQUAD fi diff -urN linux-2.5.21/arch/i386/defconfig linux/arch/i386/defconfig --- linux-2.5.21/arch/i386/defconfig Sat Jun 8 22:27:26 2002 +++ linux/arch/i386/defconfig Sun Jun 9 13:21:32 2002 @@ -74,6 +74,7 @@ # CONFIG_PREEMPT is not set # CONFIG_MULTIQUAD is not set CONFIG_HAVE_DEC_LOCK=y +CONFIG_NR_CPUS=32 # # General options diff -urN linux-2.5.21/arch/i386/kernel/smpboot.c linux/arch/i386/kernel/smpboot.c --- linux-2.5.21/arch/i386/kernel/smpboot.c Sat Jun 8 22:29:52 2002 +++ linux/arch/i386/kernel/smpboot.c Sun Jun 9 13:13:02 2002 @@ -54,7 +54,7 @@ static int smp_b_stepping; /* Setup configured maximum number of CPUs to activate */ -static int max_cpus = -1; +static int max_cpus = NR_CPUS; /* Total count of live CPUs */ int smp_num_cpus = 1; @@ -1145,7 +1145,7 @@ if (!(phys_cpu_present_map & (1 << bit))) continue; - if ((max_cpus >= 0) && (max_cpus <= cpucount+1)) + if (max_cpus <= cpucount+1) continue; do_boot_cpu(apicid); diff -urN linux-2.5.21/arch/ia64/config.in linux/arch/ia64/config.in --- linux-2.5.21/arch/ia64/config.in Sat Jun 8 22:30:07 2002 +++ linux/arch/ia64/config.in Sun Jun 9 13:24:00 2002 @@ -95,6 +95,10 @@ tristate '/proc/pal support' CONFIG_IA64_PALINFO tristate '/proc/efi/vars support' CONFIG_EFI_VARS +if [ "$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-2.5.21/arch/ia64/defconfig linux/arch/ia64/defconfig --- linux-2.5.21/arch/ia64/defconfig Sat Jun 8 22:27:16 2002 +++ linux/arch/ia64/defconfig Sun Jun 9 13:21:00 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-2.5.21/arch/mips/config.in linux/arch/mips/config.in --- linux-2.5.21/arch/mips/config.in Sat Jun 8 22:30:41 2002 +++ linux/arch/mips/config.in Sun Jun 9 13:24:57 2002 @@ -500,6 +500,8 @@ bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ if [ "$CONFIG_SMP" != "y" ]; then bool 'Run uncached' CONFIG_MIPS_UNCACHED +else + int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32 fi endmenu diff -urN linux-2.5.21/arch/mips64/config.in linux/arch/mips64/config.in --- linux-2.5.21/arch/mips64/config.in Sat Jun 8 22:27:29 2002 +++ linux/arch/mips64/config.in Sun Jun 9 13:25:12 2002 @@ -247,6 +247,8 @@ bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ if [ "$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-2.5.21/arch/mips64/defconfig linux/arch/mips64/defconfig --- linux-2.5.21/arch/mips64/defconfig Sat Jun 8 22:27:52 2002 +++ linux/arch/mips64/defconfig Sun Jun 9 13:20:17 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-2.5.21/arch/parisc/config.in linux/arch/parisc/config.in --- linux-2.5.21/arch/parisc/config.in Sat Jun 8 22:31:31 2002 +++ linux/arch/parisc/config.in Sun Jun 9 13:25:41 2002 @@ -18,6 +18,10 @@ # bool 'Symmetric multi-processing support' CONFIG_SMP define_bool CONFIG_SMP n +if [ "$CONFIG_SMP" = "y" ]; then + int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32 +fi + bool 'Kernel Debugger support' CONFIG_KWDB # define_bool CONFIG_KWDB n diff -urN linux-2.5.21/arch/ppc/config.in linux/arch/ppc/config.in --- linux-2.5.21/arch/ppc/config.in Sat Jun 8 22:26:28 2002 +++ linux/arch/ppc/config.in Sun Jun 9 13:26:29 2002 @@ -172,6 +172,7 @@ bool 'Symmetric multi-processing support' CONFIG_SMP if [ "$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 [ "$CONFIG_SMP" != "y" ]; then bool 'Preemptible Kernel' CONFIG_PREEMPT diff -urN linux-2.5.21/arch/ppc64/config.in linux/arch/ppc64/config.in --- linux-2.5.21/arch/ppc64/config.in Sat Jun 8 22:27:32 2002 +++ linux/arch/ppc64/config.in Sun Jun 9 13:26:43 2002 @@ -21,6 +21,7 @@ bool 'Symmetric multi-processing support' CONFIG_SMP if [ "$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 [ "$CONFIG_PPC_PSERIES" = "y" ]; then bool ' Hardware multithreading' CONFIG_HMT fi diff -urN linux-2.5.21/arch/ppc64/defconfig linux/arch/ppc64/defconfig --- linux-2.5.21/arch/ppc64/defconfig Sat Jun 8 22:28:19 2002 +++ linux/arch/ppc64/defconfig Sun Jun 9 13:20:43 2002 @@ -38,6 +38,7 @@ CONFIG_IRQ_ALL_CPUS=y # CONFIG_HMT is not set # CONFIG_PREEMPT is not set +CONFIG_NR_CPUS=64 # # General setup diff -urN linux-2.5.21/arch/s390/config.in linux/arch/s390/config.in --- linux-2.5.21/arch/s390/config.in Sat Jun 8 22:28:13 2002 +++ linux/arch/s390/config.in Sun Jun 9 13:27:07 2002 @@ -20,6 +20,9 @@ comment 'Processor type and features' bool 'Symmetric multi-processing support' CONFIG_SMP bool 'IEEE FPU emulation' CONFIG_MATHEMU +if [ "$CONFIG_SMP" = "y" ]; then + int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32 +fi endmenu mainmenu_option next_comment diff -urN linux-2.5.21/arch/s390/defconfig linux/arch/s390/defconfig --- linux-2.5.21/arch/s390/defconfig Sat Jun 8 22:31:19 2002 +++ linux/arch/s390/defconfig Sun Jun 9 13:40:37 2002 @@ -35,6 +35,7 @@ # CONFIG_SMP=y CONFIG_MATHEMU=y +CONFIG_NR_CPUS=64 # # Base setup diff -urN linux-2.5.21/arch/s390x/config.in linux/arch/s390x/config.in --- linux-2.5.21/arch/s390x/config.in Sat Jun 8 22:27:21 2002 +++ linux/arch/s390x/config.in Sun Jun 9 13:40:14 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-2.5.21/arch/s390x/defconfig linux/arch/s390x/defconfig --- linux-2.5.21/arch/s390x/defconfig Sat Jun 8 22:26:26 2002 +++ linux/arch/s390x/defconfig Sun Jun 9 13:40:46 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-2.5.21/arch/sparc/config.in linux/arch/sparc/config.in --- linux-2.5.21/arch/sparc/config.in Sat Jun 8 22:26:59 2002 +++ linux/arch/sparc/config.in Sun Jun 9 13:27:41 2002 @@ -17,6 +17,10 @@ bool 'Symmetric multi-processing support (does not work on sun4/sun4c)' CONFIG_SMP +if [ "$CONFIG_SMP" = "y" ]; then + int 'Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32 +fi + # Identify this as a Sparc32 build define_bool CONFIG_SPARC32 y diff -urN linux-2.5.21/arch/sparc64/config.in linux/arch/sparc64/config.in --- linux-2.5.21/arch/sparc64/config.in Sat Jun 8 22:28:44 2002 +++ linux/arch/sparc64/config.in Sun Jun 9 13:28:05 2002 @@ -17,6 +17,10 @@ bool 'Symmetric multi-processing support' CONFIG_SMP bool 'Preemptible kernel' CONFIG_PREEMPT +if [ "$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-2.5.21/arch/sparc64/defconfig linux/arch/sparc64/defconfig --- linux-2.5.21/arch/sparc64/defconfig Sat Jun 8 22:28:49 2002 +++ linux/arch/sparc64/defconfig Sun Jun 9 13:21:45 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-2.5.21/arch/x86_64/config.in linux/arch/x86_64/config.in --- linux-2.5.21/arch/x86_64/config.in Sat Jun 8 22:28:13 2002 +++ linux/arch/x86_64/config.in Sun Jun 9 13:28:46 2002 @@ -45,8 +45,11 @@ #bool 'MTRR (Memory Type Range Register) support' CONFIG_MTRR bool 'Symmetric multi-processing support' CONFIG_SMP bool 'Preemptible Kernel' CONFIG_PREEMPT -if [ "$CONFIG_SMP" = "y" -a "$CONFIG_X86_CMPXCHG" = "y" ]; then - define_bool CONFIG_HAVE_DEC_LOCK y +if [ "$CONFIG_SMP" = "y" ]; then + int 'Maximum number of CPUs (2-64)' CONFIG_NR_CPUS 64 + if [ "$CONFIG_X86_CMPXCHG" = "y" ]; then + define_bool CONFIG_HAVE_DEC_LOCK y + fi fi define_bool CONFIG_X86_MCE y diff -urN linux-2.5.21/arch/x86_64/defconfig linux/arch/x86_64/defconfig --- linux-2.5.21/arch/x86_64/defconfig Sat Jun 8 22:30:52 2002 +++ linux/arch/x86_64/defconfig Sun Jun 9 13:20:30 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 # # General options diff -urN linux-2.5.21/include/linux/threads.h linux/include/linux/threads.h --- linux-2.5.21/include/linux/threads.h Sat Jun 8 22:26:49 2002 +++ linux/include/linux/threads.h Sun Jun 9 13:16:29 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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ Next message: Oliver Neukum: "Re: PCI DMA to small buffers on cache-incoherent arch" Previous message: Ingo Molnar: "[patch] current scheduler bits #2, 2.5.21" Next in thread: Randy.Dunlap: "Re: [PATCH] CONFIG_NR_CPUS, redux" Reply: Randy.Dunlap: "Re: [PATCH] CONFIG_NR_CPUS, redux" Reply: Rob Radez: "Re: [PATCH] CONFIG_NR_CPUS, redux" Maybe reply: Matt_Domsch@Dell.com: "RE: [PATCH] CONFIG_NR_CPUS, redux" Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] This archive was generated by hypermail 2b29 : Sat Jun 15 2002 - 22:00:23 EST
