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[PATCH] x86_64: Don't reserve hotplug CPUs by default

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Most users don't need it so no need to waste memory.
This means an user has to specify the appropiate number of
hotplug CPUs on the command line with additional_cpus=...
or fix their BIOS to follow the convention in
Documentation/x86-64/cpu-hotplug-spec

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andi Kleen 2006-01-11 22:42:35 +01:00 committed by Linus Torvalds
parent 92934bcbf9
commit f62a91f691
2 changed files with 5 additions and 8 deletions
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2
Documentation/x86_64/boot-options.txt
View File

@ -125,7 +125,7 @@ SMP
cpumask=MASK only use cpus with bits set in mask cpumask=MASK only use cpus with bits set in mask
additional_cpus=NUM Allow NUM more CPUs for hotplug 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 NUMA

11
arch/x86_64/kernel/smpboot.c
View File

@ -927,8 +927,8 @@ int additional_cpus __initdata = -1;
* *
* Three ways to find out the number of additional hotplug CPUs: * Three ways to find out the number of additional hotplug CPUs:
* - If the BIOS specified disabled CPUs in ACPI/mptables use that. * - 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 * - 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. * We do this because additional CPUs waste a lot of memory.
* -AK * -AK
*/ */
@ -938,13 +938,10 @@ __init void prefill_possible_map(void)
int possible; int possible;
if (additional_cpus == -1) { if (additional_cpus == -1) {
if (disabled_cpus > 0) { if (disabled_cpus > 0)
additional_cpus = disabled_cpus; additional_cpus = disabled_cpus;
} else { else
additional_cpus = num_processors / 2; additional_cpus = 0;
if (additional_cpus == 0)
additional_cpus = 2;
}
} }
possible = num_processors + additional_cpus; possible = num_processors + additional_cpus;
if (possible > NR_CPUS) if (possible > NR_CPUS)