From 255acee706b333b79f593dd366f16e1f107cccc3 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Fri, 17 Feb 2006 13:52:46 -0800 Subject: [PATCH] s390: additional_cpus parameter Introduce additional_cpus command line option. By default no additional cpu can be attached to the system anymore. Only the cpus present at IPL time can be switched on/off. If it is desired that additional cpus can be attached to the system the maximum number of additional cpus needs to be specified with this option. This change is necessary in order to limit the waste of per_cpu data structures. Signed-off-by: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/cpu-hotplug.txt | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'Documentation') diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index e05278087ffa..4d3355da0e26 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -11,6 +11,8 @@ Joel Schopp ia64/x86_64: Ashok Raj + s390: + Heiko Carstens Authors: Ashok Raj Lots of feedback: Nathan Lynch , @@ -44,11 +46,9 @@ maxcpus=n Restrict boot time cpus to n. Say if you have 4 cpus, using maxcpus=2 will only boot 2. You can choose to bring the other cpus later online, read FAQ's for more info. -additional_cpus*=n Use this to limit hotpluggable cpus. This option sets - cpu_possible_map = cpu_present_map + additional_cpus - -(*) Option valid only for following architectures -- x86_64, ia64 +additional_cpus=n [x86_64, s390 only] use this to limit hotpluggable cpus. + This option sets + cpu_possible_map = cpu_present_map + additional_cpus ia64 and x86_64 use the number of disabled local apics in ACPI tables MADT to determine the number of potentially hot-pluggable cpus. The implementation -- cgit v1.2.3 From 37a3302618a51520e2056494715ea6b4776dd8ab Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Fri, 17 Feb 2006 13:52:47 -0800 Subject: [PATCH] s390: possible_cpus parameter Introduce possible_cpus command line option. Hard sets the number of bits set in cpu_possible_map. Unlike the additional_cpus parameter this one guarantees that num_possible_cpus() will stay constant even if the system gets rebooted and a different number of cpus are present at startup. Signed-off-by: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/cpu-hotplug.txt | 6 ++++++ arch/s390/kernel/smp.c | 14 +++++++++++--- 2 files changed, 17 insertions(+), 3 deletions(-) (limited to 'Documentation') diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index 4d3355da0e26..e71bc6cbbc5e 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -58,6 +58,12 @@ mark such hot-pluggable cpus as disabled entries, one could use this parameter "additional_cpus=x" to represent those cpus in the cpu_possible_map. +possible_cpus=n [s390 only] use this to set hotpluggable cpus. + This option sets possible_cpus bits in + cpu_possible_map. Thus keeping the numbers of bits set + constant even if the machine gets rebooted. + This option overrides additional_cpus. + CPU maps and such ----------------- [More on cpumaps and primitive to manipulate, please check diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index 53291e94ac7b..d0a2745aec7f 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -673,15 +673,16 @@ __cpu_up(unsigned int cpu) } static unsigned int __initdata additional_cpus; +static unsigned int __initdata possible_cpus; void __init smp_setup_cpu_possible_map(void) { unsigned int pcpus, cpu; - pcpus = smp_count_cpus() + additional_cpus; + pcpus = min(smp_count_cpus() + additional_cpus, (unsigned int) NR_CPUS); - if (pcpus > NR_CPUS) - pcpus = NR_CPUS; + if (possible_cpus) + pcpus = min(possible_cpus, (unsigned int) NR_CPUS); for (cpu = 0; cpu < pcpus; cpu++) cpu_set(cpu, cpu_possible_map); @@ -698,6 +699,13 @@ static int __init setup_additional_cpus(char *s) } early_param("additional_cpus", setup_additional_cpus); +static int __init setup_possible_cpus(char *s) +{ + possible_cpus = simple_strtoul(s, NULL, 0); + return 0; +} +early_param("possible_cpus", setup_possible_cpus); + int __cpu_disable(void) { -- cgit v1.2.3