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-rw-r--r--Documentation/x86_64/boot-options.txt2
-rw-r--r--arch/x86_64/kernel/smpboot.c11
2 files changed, 5 insertions, 8 deletions
diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt
index e566affeed7..72ab9b99b22 100644
--- a/Documentation/x86_64/boot-options.txt
+++ b/Documentation/x86_64/boot-options.txt
@@ -125,7 +125,7 @@ SMP
cpumask=MASK only use cpus with bits set in mask
additional_cpus=NUM Allow NUM more CPUs for hotplug
- (defaults are specified by the BIOS or half the available CPUs)
+ (defaults are specified by the BIOS, see Documentation/x86_64/cpu-hotplug-spec)
NUMA
diff --git a/arch/x86_64/kernel/smpboot.c b/arch/x86_64/kernel/smpboot.c
index ecbd7b83acc..043b1d262a3 100644
--- a/arch/x86_64/kernel/smpboot.c
+++ b/arch/x86_64/kernel/smpboot.c
@@ -927,8 +927,8 @@ int additional_cpus __initdata = -1;
*
* Three ways to find out the number of additional hotplug CPUs:
* - If the BIOS specified disabled CPUs in ACPI/mptables use that.
- * - otherwise use half of the available CPUs or 2, whatever is more.
* - The user can overwrite it with additional_cpus=NUM
+ * - Otherwise don't reserve additional CPUs.
* We do this because additional CPUs waste a lot of memory.
* -AK
*/
@@ -938,13 +938,10 @@ __init void prefill_possible_map(void)
int possible;
if (additional_cpus == -1) {
- if (disabled_cpus > 0) {
+ if (disabled_cpus > 0)
additional_cpus = disabled_cpus;
- } else {
- additional_cpus = num_processors / 2;
- if (additional_cpus == 0)
- additional_cpus = 2;
- }
+ else
+ additional_cpus = 0;
}
possible = num_processors + additional_cpus;
if (possible > NR_CPUS)