Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.
1 =========================================== 2 How CPU topology info is exported via sysfs 3 =========================================== 4 5 Export CPU topology info via sysfs. Items (attributes) are similar 6 to /proc/cpuinfo output of some architectures: 7 8 1) /sys/devices/system/cpu/cpuX/topology/physical_package_id: 9 10 physical package id of cpuX. Typically corresponds to a physical 11 socket number, but the actual value is architecture and platform 12 dependent. 13 14 2) /sys/devices/system/cpu/cpuX/topology/core_id: 15 16 the CPU core ID of cpuX. Typically it is the hardware platform's 17 identifier (rather than the kernel's). The actual value is 18 architecture and platform dependent. 19 20 3) /sys/devices/system/cpu/cpuX/topology/book_id: 21 22 the book ID of cpuX. Typically it is the hardware platform's 23 identifier (rather than the kernel's). The actual value is 24 architecture and platform dependent. 25 26 4) /sys/devices/system/cpu/cpuX/topology/drawer_id: 27 28 the drawer ID of cpuX. Typically it is the hardware platform's 29 identifier (rather than the kernel's). The actual value is 30 architecture and platform dependent. 31 32 5) /sys/devices/system/cpu/cpuX/topology/thread_siblings: 33 34 internal kernel map of cpuX's hardware threads within the same 35 core as cpuX. 36 37 6) /sys/devices/system/cpu/cpuX/topology/thread_siblings_list: 38 39 human-readable list of cpuX's hardware threads within the same 40 core as cpuX. 41 42 7) /sys/devices/system/cpu/cpuX/topology/core_siblings: 43 44 internal kernel map of cpuX's hardware threads within the same 45 physical_package_id. 46 47 8) /sys/devices/system/cpu/cpuX/topology/core_siblings_list: 48 49 human-readable list of cpuX's hardware threads within the same 50 physical_package_id. 51 52 9) /sys/devices/system/cpu/cpuX/topology/book_siblings: 53 54 internal kernel map of cpuX's hardware threads within the same 55 book_id. 56 57 10) /sys/devices/system/cpu/cpuX/topology/book_siblings_list: 58 59 human-readable list of cpuX's hardware threads within the same 60 book_id. 61 62 11) /sys/devices/system/cpu/cpuX/topology/drawer_siblings: 63 64 internal kernel map of cpuX's hardware threads within the same 65 drawer_id. 66 67 12) /sys/devices/system/cpu/cpuX/topology/drawer_siblings_list: 68 69 human-readable list of cpuX's hardware threads within the same 70 drawer_id. 71 72 To implement it in an architecture-neutral way, a new source file, 73 drivers/base/topology.c, is to export the 6 to 12 attributes. The book 74 and drawer related sysfs files will only be created if CONFIG_SCHED_BOOK 75 and CONFIG_SCHED_DRAWER are selected. 76 77 CONFIG_SCHED_BOOK and CONFIG_DRAWER are currently only used on s390, where 78 they reflect the cpu and cache hierarchy. 79 80 For an architecture to support this feature, it must define some of 81 these 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 92 The type of ``**_id macros`` is int. 93 The type of ``**_cpumask macros`` is ``(const) struct cpumask *``. The latter 94 correspond with appropriate ``**_siblings`` sysfs attributes (except for 95 topology_sibling_cpumask() which corresponds with thread_siblings). 96 97 To be consistent on all architectures, include/linux/topology.h 98 provides default definitions for any of the above macros that are 99 not defined by include/asm-XXX/topology.h: 100 101 1) physical_package_id: -1 102 2) core_id: 0 103 3) sibling_cpumask: just the given CPU 104 4) core_cpumask: just the given CPU 105 106 For architectures that don't support books (CONFIG_SCHED_BOOK) there are no 107 default definitions for topology_book_id() and topology_book_cpumask(). 108 For architectures that don't support drawers (CONFIG_SCHED_DRAWER) there are 109 no default definitions for topology_drawer_id() and topology_drawer_cpumask(). 110 111 Additionally, CPU topology information is provided under 112 /sys/devices/system/cpu and includes these files. The internal 113 source 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 =========== ========================================================== 132 133 The format for the above output is compatible with cpulist_parse() 134 [see <linux/cpumask.h>]. Some examples follow. 135 136 In this example, there are 64 CPUs in the system but cpus 32-63 exceed 137 the kernel max which is limited to 0..31 by the NR_CPUS config option 138 being 32. Note also that CPUs 2 and 4-31 are not online but could be 139 brought 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: 0-31 146 147 In this example, the NR_CPUS config option is 128, but the kernel was 148 started with possible_cpus=144. There are 4 CPUs in the system and cpu2 149 was manually taken offline (and is the only CPU that can be brought 150 online.):: 151 152 kernel_max: 127 153 offline: 2,4-127,128-143 154 online: 0-1,3 155 possible: 0-127 156 present: 0-3 157 158 See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter 159 as well as more information on the various cpumasks.
