Commit 2b633e3fac5efada088b57d31e65401f22bcc18f
Committed by
H. Peter Anvin
H. Peter Anvin
1 parent
6738762d73
Exists in
master
and in
4 other branches
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 <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>
Showing 5 changed files with 28 additions and 7 deletions Side-by-side Diff
Documentation/kernel-parameters.txt
| ... | ... | @@ -1772,6 +1772,12 @@ |
| 1772 | 1772 | purges which is reported from either PAL_VM_SUMMARY or |
| 1773 | 1773 | SAL PALO. |
| 1774 | 1774 | |
| 1775 | + nr_cpus= [SMP] Maximum number of processors that an SMP kernel | |
| 1776 | + could support. nr_cpus=n : n >= 1 limits the kernel to | |
| 1777 | + supporting 'n' processors. Later in runtime you can not | |
| 1778 | + use hotplug cpu feature to put more cpu back to online. | |
| 1779 | + just like you compile the kernel NR_CPUS=n | |
| 1780 | + | |
| 1775 | 1781 | nr_uarts= [SERIAL] maximum number of UARTs to be registered. |
| 1776 | 1782 | |
| 1777 | 1783 | numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. |
arch/ia64/kernel/acpi.c
| ... | ... | @@ -881,8 +881,8 @@ |
| 881 | 881 | |
| 882 | 882 | possible = available_cpus + additional_cpus; |
| 883 | 883 | |
| 884 | - if (possible > NR_CPUS) | |
| 885 | - possible = NR_CPUS; | |
| 884 | + if (possible > nr_cpu_ids) | |
| 885 | + possible = nr_cpu_ids; | |
| 886 | 886 | |
| 887 | 887 | printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n", |
| 888 | 888 | possible, max((possible - available_cpus), 0)); |
arch/x86/kernel/smpboot.c
| ... | ... | @@ -1213,11 +1213,12 @@ |
| 1213 | 1213 | |
| 1214 | 1214 | total_cpus = max_t(int, possible, num_processors + disabled_cpus); |
| 1215 | 1215 | |
| 1216 | - if (possible > CONFIG_NR_CPUS) { | |
| 1216 | + /* nr_cpu_ids could be reduced via nr_cpus= */ | |
| 1217 | + if (possible > nr_cpu_ids) { | |
| 1217 | 1218 | printk(KERN_WARNING |
| 1218 | 1219 | "%d Processors exceeds NR_CPUS limit of %d\n", |
| 1219 | - possible, CONFIG_NR_CPUS); | |
| 1220 | - possible = CONFIG_NR_CPUS; | |
| 1220 | + possible, nr_cpu_ids); | |
| 1221 | + possible = nr_cpu_ids; | |
| 1221 | 1222 | } |
| 1222 | 1223 | |
| 1223 | 1224 | printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n", |
drivers/acpi/numa.c
| ... | ... | @@ -279,9 +279,9 @@ |
| 279 | 279 | /* SRAT: Static Resource Affinity Table */ |
| 280 | 280 | if (!acpi_table_parse(ACPI_SIG_SRAT, acpi_parse_srat)) { |
| 281 | 281 | acpi_table_parse_srat(ACPI_SRAT_TYPE_X2APIC_CPU_AFFINITY, |
| 282 | - acpi_parse_x2apic_affinity, NR_CPUS); | |
| 282 | + acpi_parse_x2apic_affinity, nr_cpu_ids); | |
| 283 | 283 | acpi_table_parse_srat(ACPI_SRAT_TYPE_CPU_AFFINITY, |
| 284 | - acpi_parse_processor_affinity, NR_CPUS); | |
| 284 | + acpi_parse_processor_affinity, nr_cpu_ids); | |
| 285 | 285 | ret = acpi_table_parse_srat(ACPI_SRAT_TYPE_MEMORY_AFFINITY, |
| 286 | 286 | acpi_parse_memory_affinity, |
| 287 | 287 | NR_NODE_MEMBLKS); |
init/main.c
| ... | ... | @@ -149,6 +149,20 @@ |
| 149 | 149 | |
| 150 | 150 | early_param("nosmp", nosmp); |
| 151 | 151 | |
| 152 | +/* this is hard limit */ | |
| 153 | +static int __init nrcpus(char *str) | |
| 154 | +{ | |
| 155 | + int nr_cpus; | |
| 156 | + | |
| 157 | + get_option(&str, &nr_cpus); | |
| 158 | + if (nr_cpus > 0 && nr_cpus < nr_cpu_ids) | |
| 159 | + nr_cpu_ids = nr_cpus; | |
| 160 | + | |
| 161 | + return 0; | |
| 162 | +} | |
| 163 | + | |
| 164 | +early_param("nr_cpus", nrcpus); | |
| 165 | + | |
| 152 | 166 | static int __init maxcpus(char *str) |
| 153 | 167 | { |
| 154 | 168 | get_option(&str, &setup_max_cpus); |