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smp: Use nr_cpus= to set nr_cpu_ids early

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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 <yinghai@kernel.org>
LKML-Reference: <1265793639-15071-34-git-send-email-yinghai@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Yinghai Lu 2010-02-10 01:20:37 -08:00 committed by H. Peter Anvin
parent 6738762d73
commit 2b633e3fac
5 changed files with 28 additions and 7 deletions
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6
Documentation/kernel-parameters.txt
View file

@ -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.

4
arch/ia64/kernel/acpi.c
View file

@ -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));

7
arch/x86/kernel/smpboot.c
View file

@ -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",

4
drivers/acpi/numa.c
View file

@ -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);

14
init/main.c
View file

@ -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);