X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=Documentation%2Fcpu-hotplug.txt;h=1bcf69996c9df74fba87c25949c05285ff604d3b;hb=9becde79d2c5e382d955167c07017b5e34b142f0;hp=e05278087ffaa04c90afd11bf85ff5629f814507;hpb=e7f52e4c43ba5d59a08c8482b5cf1f20f1ce7664;p=linux-2.6-omap-h63xx.git diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index e05278087ff..1bcf69996c9 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 , @@ -45,10 +47,10 @@ maxcpus=n Restrict boot time cpus to n. Say if you have 4 cpus, using 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 + cpu_possible_map = cpu_present_map + additional_cpus (*) Option valid only for following architectures -- x86_64, ia64 +- x86_64, ia64, s390 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 @@ -57,6 +59,15 @@ apicid values in those tables for disabled apics. In the event BIOS doesnt 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. +s390 uses the number of cpus it detects at IPL time to also the number of bits +in cpu_possible_map. If it is desired to add additional cpus at a later time +the number should be specified using this option or the possible_cpus option. + +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 ----------------- @@ -86,13 +97,13 @@ at which time hotplug is disabled. You really dont need to manipulate any of the system cpu maps. They should be read-only for most use. When setting up per-cpu resources almost always use -cpu_possible_map/for_each_cpu() to iterate. +cpu_possible_map/for_each_possible_cpu() to iterate. Never use anything other than cpumask_t to represent bitmap of CPUs. #include -for_each_cpu - Iterate over cpu_possible_map +for_each_possible_cpu - Iterate over cpu_possible_map for_each_online_cpu - Iterate over cpu_online_map for_each_present_cpu - Iterate over cpu_present_map for_each_cpu_mask(x,mask) - Iterate over some random collection of cpu mask.