From 2b633e3fac5efada088b57d31e65401f22bcc18f Mon Sep 17 00:00:00 2001 From: Yinghai Lu Date: Wed, 10 Feb 2010 01:20:37 -0800 Subject: [PATCH] smp: Use nr_cpus= to set nr_cpu_ids early On x86, before prefill_possible_map(), nr_cpu_ids will be NR_CPUS aka CONFIG_NR_CPUS. Add nr_cpus= to set nr_cpu_ids. so we can simulate cpus <=8 are installed on normal config. -v2: accordging to Christoph, acpi_numa_init should use nr_cpu_ids in stead of NR_CPUS. -v3: add doc in kernel-parameters.txt according to Andrew. Signed-off-by: Yinghai Lu LKML-Reference: <1265793639-15071-34-git-send-email-yinghai@kernel.org> Acked-by: Linus Torvalds Signed-off-by: H. Peter Anvin Cc: Tony Luck --- Documentation/kernel-parameters.txt | 6 ++++++ arch/ia64/kernel/acpi.c | 4 ++-- arch/x86/kernel/smpboot.c | 7 ++++--- drivers/acpi/numa.c | 4 ++-- init/main.c | 14 ++++++++++++++ 5 files changed, 28 insertions(+), 7 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 736d4560288..51bceb0fb27 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1772,6 +1772,12 @@ and is between 256 and 4096 characters. It is defined in the file purges which is reported from either PAL_VM_SUMMARY or SAL PALO. + nr_cpus= [SMP] Maximum number of processors that an SMP kernel + could support. nr_cpus=n : n >= 1 limits the kernel to + supporting 'n' processors. Later in runtime you can not + use hotplug cpu feature to put more cpu back to online. + just like you compile the kernel NR_CPUS=n + nr_uarts= [SERIAL] maximum number of UARTs to be registered. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. diff --git a/arch/ia64/kernel/acpi.c b/arch/ia64/kernel/acpi.c index 40574ae1140..605a08b2972 100644 --- a/arch/ia64/kernel/acpi.c +++ b/arch/ia64/kernel/acpi.c @@ -881,8 +881,8 @@ __init void prefill_possible_map(void) possible = available_cpus + additional_cpus; - if (possible > NR_CPUS) - possible = NR_CPUS; + if (possible > nr_cpu_ids) + possible = nr_cpu_ids; printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n", possible, max((possible - available_cpus), 0)); diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 678d0b8c26f..eff2fe17542 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1213,11 +1213,12 @@ __init void prefill_possible_map(void) total_cpus = max_t(int, possible, num_processors + disabled_cpus); - if (possible > CONFIG_NR_CPUS) { + /* nr_cpu_ids could be reduced via nr_cpus= */ + if (possible > nr_cpu_ids) { printk(KERN_WARNING "%d Processors exceeds NR_CPUS limit of %d\n", - possible, CONFIG_NR_CPUS); - possible = CONFIG_NR_CPUS; + possible, nr_cpu_ids); + possible = nr_cpu_ids; } printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n", diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c index 7ad48dfc12d..b8725461d88 100644 --- a/drivers/acpi/numa.c +++ b/drivers/acpi/numa.c @@ -279,9 +279,9 @@ int __init acpi_numa_init(void) /* SRAT: Static Resource Affinity Table */ if (!acpi_table_parse(ACPI_SIG_SRAT, acpi_parse_srat)) { acpi_table_parse_srat(ACPI_SRAT_TYPE_X2APIC_CPU_AFFINITY, - acpi_parse_x2apic_affinity, NR_CPUS); + acpi_parse_x2apic_affinity, nr_cpu_ids); acpi_table_parse_srat(ACPI_SRAT_TYPE_CPU_AFFINITY, - acpi_parse_processor_affinity, NR_CPUS); + acpi_parse_processor_affinity, nr_cpu_ids); ret = acpi_table_parse_srat(ACPI_SRAT_TYPE_MEMORY_AFFINITY, acpi_parse_memory_affinity, NR_NODE_MEMBLKS); diff --git a/init/main.c b/init/main.c index 845187822e5..05b5283e98f 100644 --- a/init/main.c +++ b/init/main.c @@ -149,6 +149,20 @@ static int __init nosmp(char *str) early_param("nosmp", nosmp); +/* this is hard limit */ +static int __init nrcpus(char *str) +{ + int nr_cpus; + + get_option(&str, &nr_cpus); + if (nr_cpus > 0 && nr_cpus < nr_cpu_ids) + nr_cpu_ids = nr_cpus; + + return 0; +} + +early_param("nr_cpus", nrcpus); + static int __init maxcpus(char *str) { get_option(&str, &setup_max_cpus); -- 2.39.3