diff options
Diffstat (limited to 'Documentation/cputopology.txt')
| -rw-r--r-- | Documentation/cputopology.txt | 54 |
1 files changed, 51 insertions, 3 deletions
diff --git a/Documentation/cputopology.txt b/Documentation/cputopology.txt index bd699da24666..b41f3e58aefa 100644 --- a/Documentation/cputopology.txt +++ b/Documentation/cputopology.txt @@ -18,11 +18,11 @@ For an architecture to support this feature, it must define some of these macros in include/asm-XXX/topology.h: #define topology_physical_package_id(cpu) #define topology_core_id(cpu) -#define topology_thread_siblings(cpu) -#define topology_core_siblings(cpu) +#define topology_thread_cpumask(cpu) +#define topology_core_cpumask(cpu) The type of **_id is int. -The type of siblings is cpumask_t. +The type of siblings is (const) struct cpumask *. To be consistent on all architectures, include/linux/topology.h provides default definitions for any of the above macros that are @@ -31,3 +31,51 @@ not defined by include/asm-XXX/topology.h: 2) core_id: 0 3) thread_siblings: just the given CPU 4) core_siblings: just the given CPU + +Additionally, cpu topology information is provided under +/sys/devices/system/cpu and includes these files. The internal +source for the output is in brackets ("[]"). + + kernel_max: the maximum cpu index allowed by the kernel configuration. + [NR_CPUS-1] + + offline: cpus that are not online because they have been + HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit + of cpus allowed by the kernel configuration (kernel_max + above). [~cpu_online_mask + cpus >= NR_CPUS] + + online: cpus that are online and being scheduled [cpu_online_mask] + + possible: cpus that have been allocated resources and can be + brought online if they are present. [cpu_possible_mask] + + present: cpus that have been identified as being present in the + system. [cpu_present_mask] + +The format for the above output is compatible with cpulist_parse() +[see <linux/cpumask.h>]. Some examples follow. + +In this example, there are 64 cpus in the system but cpus 32-63 exceed +the kernel max which is limited to 0..31 by the NR_CPUS config option +being 32. Note also that cpus 2 and 4-31 are not online but could be +brought online as they are both present and possible. + + kernel_max: 31 + offline: 2,4-31,32-63 + online: 0-1,3 + possible: 0-31 + present: 0-31 + +In this example, the NR_CPUS config option is 128, but the kernel was +started with possible_cpus=144. There are 4 cpus in the system and cpu2 +was manually taken offline (and is the only cpu that can be brought +online.) + + kernel_max: 127 + offline: 2,4-127,128-143 + online: 0-1,3 + possible: 0-127 + present: 0-3 + +See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter +as well as more information on the various cpumask's. |