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x86: use possible_cpus=NUM to extend the possible cpus allowed

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Impact: add new boot parameter

Use possible_cpus=NUM kernel parameter to extend the number of possible
cpus.

The ability to HOTPLUG ON cpus that are "possible" but not "present" is
dealt with in a later patch.

Signed-off-by: Mike Travis <travis@sgi.com>
This commit is contained in:
Mike Travis
2008-12-17 15:21:39 -08:00
committed by Ingo Molnar
parent a775a38b13
commit 3b11ce7f54
3 changed files with 42 additions and 20 deletions
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25
arch/x86/kernel/smpboot.c
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@@ -1252,6 +1252,15 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
check_nmi_watchdog();
}
static int __initdata setup_possible_cpus = -1;
static int __init _setup_possible_cpus(char *str)
{
get_option(&str, &setup_possible_cpus);
return 0;
}
early_param("possible_cpus", _setup_possible_cpus);
/*
* cpu_possible_map should be static, it cannot change as cpu's
* are onlined, or offlined. The reason is per-cpu data-structures
@@ -1264,7 +1273,7 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
*
* Three ways to find out the number of additional hotplug CPUs:
* - If the BIOS specified disabled CPUs in ACPI/mptables use that.
* - The user can overwrite it with additional_cpus=NUM
* - The user can overwrite it with possible_cpus=NUM
* - Otherwise don't reserve additional CPUs.
* We do this because additional CPUs waste a lot of memory.
* -AK
@@ -1277,9 +1286,17 @@ __init void prefill_possible_map(void)
if (!num_processors)
num_processors = 1;
possible = num_processors + disabled_cpus;
if (possible > NR_CPUS)
possible = NR_CPUS;
if (setup_possible_cpus == -1)
possible = num_processors + disabled_cpus;
else
possible = setup_possible_cpus;
if (possible > CONFIG_NR_CPUS) {
printk(KERN_WARNING
"%d Processors exceeds NR_CPUS limit of %d\n",
possible, CONFIG_NR_CPUS);
possible = CONFIG_NR_CPUS;
}
printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n",
possible, max_t(int, possible - num_processors, 0));