1=========================================== 2How CPU topology info is exported via sysfs 3=========================================== 4 5Export CPU topology info via sysfs. Items (attributes) are similar 6to /proc/cpuinfo output of some architectures. They reside in 7/sys/devices/system/cpu/cpuX/topology/: 8 9physical_package_id: 10 11 physical package id of cpuX. Typically corresponds to a physical 12 socket number, but the actual value is architecture and platform 13 dependent. 14 15core_id: 16 17 the CPU core ID of cpuX. Typically it is the hardware platform's 18 identifier (rather than the kernel's). The actual value is 19 architecture and platform dependent. 20 21book_id: 22 23 the book ID of cpuX. Typically it is the hardware platform's 24 identifier (rather than the kernel's). The actual value is 25 architecture and platform dependent. 26 27drawer_id: 28 29 the drawer ID of cpuX. Typically it is the hardware platform's 30 identifier (rather than the kernel's). The actual value is 31 architecture and platform dependent. 32 33thread_siblings: 34 35 internal kernel map of cpuX's hardware threads within the same 36 core as cpuX. 37 38thread_siblings_list: 39 40 human-readable list of cpuX's hardware threads within the same 41 core as cpuX. 42 43core_siblings: 44 45 internal kernel map of cpuX's hardware threads within the same 46 physical_package_id. 47 48core_siblings_list: 49 50 human-readable list of cpuX's hardware threads within the same 51 physical_package_id. 52 53book_siblings: 54 55 internal kernel map of cpuX's hardware threads within the same 56 book_id. 57 58book_siblings_list: 59 60 human-readable list of cpuX's hardware threads within the same 61 book_id. 62 63drawer_siblings: 64 65 internal kernel map of cpuX's hardware threads within the same 66 drawer_id. 67 68drawer_siblings_list: 69 70 human-readable list of cpuX's hardware threads within the same 71 drawer_id. 72 73Architecture-neutral, drivers/base/topology.c, exports these attributes. 74However, the book and drawer related sysfs files will only be created if 75CONFIG_SCHED_BOOK and CONFIG_SCHED_DRAWER are selected, respectively. 76 77CONFIG_SCHED_BOOK and CONFIG_SCHED_DRAWER are currently only used on s390, 78where they reflect the cpu and cache hierarchy. 79 80For an architecture to support this feature, it must define some of 81these macros in include/asm-XXX/topology.h:: 82 83 #define topology_physical_package_id(cpu) 84 #define topology_core_id(cpu) 85 #define topology_book_id(cpu) 86 #define topology_drawer_id(cpu) 87 #define topology_sibling_cpumask(cpu) 88 #define topology_core_cpumask(cpu) 89 #define topology_book_cpumask(cpu) 90 #define topology_drawer_cpumask(cpu) 91 92The type of ``**_id macros`` is int. 93The type of ``**_cpumask macros`` is ``(const) struct cpumask *``. The latter 94correspond with appropriate ``**_siblings`` sysfs attributes (except for 95topology_sibling_cpumask() which corresponds with thread_siblings). 96 97To be consistent on all architectures, include/linux/topology.h 98provides default definitions for any of the above macros that are 99not defined by include/asm-XXX/topology.h: 100 1011) topology_physical_package_id: -1 1022) topology_core_id: 0 1033) topology_sibling_cpumask: just the given CPU 1044) topology_core_cpumask: just the given CPU 105 106For architectures that don't support books (CONFIG_SCHED_BOOK) there are no 107default definitions for topology_book_id() and topology_book_cpumask(). 108For architectures that don't support drawers (CONFIG_SCHED_DRAWER) there are 109no default definitions for topology_drawer_id() and topology_drawer_cpumask(). 110 111Additionally, CPU topology information is provided under 112/sys/devices/system/cpu and includes these files. The internal 113source for the output is in brackets ("[]"). 114 115 =========== ========================================================== 116 kernel_max: the maximum CPU index allowed by the kernel configuration. 117 [NR_CPUS-1] 118 119 offline: CPUs that are not online because they have been 120 HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit 121 of CPUs allowed by the kernel configuration (kernel_max 122 above). [~cpu_online_mask + cpus >= NR_CPUS] 123 124 online: CPUs that are online and being scheduled [cpu_online_mask] 125 126 possible: CPUs that have been allocated resources and can be 127 brought online if they are present. [cpu_possible_mask] 128 129 present: CPUs that have been identified as being present in the 130 system. [cpu_present_mask] 131 =========== ========================================================== 132 133The format for the above output is compatible with cpulist_parse() 134[see <linux/cpumask.h>]. Some examples follow. 135 136In this example, there are 64 CPUs in the system but cpus 32-63 exceed 137the kernel max which is limited to 0..31 by the NR_CPUS config option 138being 32. Note also that CPUs 2 and 4-31 are not online but could be 139brought online as they are both present and possible:: 140 141 kernel_max: 31 142 offline: 2,4-31,32-63 143 online: 0-1,3 144 possible: 0-31 145 present: 0-31 146 147In this example, the NR_CPUS config option is 128, but the kernel was 148started with possible_cpus=144. There are 4 CPUs in the system and cpu2 149was manually taken offline (and is the only CPU that can be brought 150online.):: 151 152 kernel_max: 127 153 offline: 2,4-127,128-143 154 online: 0-1,3 155 possible: 0-127 156 present: 0-3 157 158See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter 159as well as more information on the various cpumasks. 160