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e8cb6f1e MCC |
1 | =========================================== |
2 | How CPU topology info is exported via sysfs | |
3 | =========================================== | |
69dcc991 | 4 | |
663fb2fc | 5 | Export CPU topology info via sysfs. Items (attributes) are similar |
3a1c779f LB |
6 | to /proc/cpuinfo output of some architectures. They reside in |
7 | /sys/devices/system/cpu/cpuX/topology/: | |
69dcc991 | 8 | |
3a1c779f | 9 | physical_package_id: |
663fb2fc AC |
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 | ||
3a1c779f | 15 | core_id: |
663fb2fc AC |
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 | ||
3a1c779f | 21 | book_id: |
b40d8ed4 HC |
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 | ||
3a1c779f | 27 | drawer_id: |
a62247e1 HC |
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 | ||
3a1c779f | 33 | thread_siblings: |
663fb2fc | 34 | |
f8ea61e6 | 35 | internal kernel map of cpuX's hardware threads within the same |
54a53694 | 36 | core as cpuX. |
663fb2fc | 37 | |
3a1c779f | 38 | thread_siblings_list: |
54a53694 BG |
39 | |
40 | human-readable list of cpuX's hardware threads within the same | |
41 | core as cpuX. | |
42 | ||
3a1c779f | 43 | core_siblings: |
663fb2fc AC |
44 | |
45 | internal kernel map of cpuX's hardware threads within the same | |
46 | physical_package_id. | |
69dcc991 | 47 | |
3a1c779f | 48 | core_siblings_list: |
54a53694 BG |
49 | |
50 | human-readable list of cpuX's hardware threads within the same | |
51 | physical_package_id. | |
52 | ||
3a1c779f | 53 | book_siblings: |
b40d8ed4 HC |
54 | |
55 | internal kernel map of cpuX's hardware threads within the same | |
56 | book_id. | |
57 | ||
3a1c779f | 58 | book_siblings_list: |
54a53694 BG |
59 | |
60 | human-readable list of cpuX's hardware threads within the same | |
61 | book_id. | |
62 | ||
3a1c779f | 63 | drawer_siblings: |
a62247e1 HC |
64 | |
65 | internal kernel map of cpuX's hardware threads within the same | |
66 | drawer_id. | |
67 | ||
3a1c779f | 68 | drawer_siblings_list: |
a62247e1 HC |
69 | |
70 | human-readable list of cpuX's hardware threads within the same | |
71 | drawer_id. | |
72 | ||
3a1c779f LB |
73 | Architecture-neutral, drivers/base/topology.c, exports these attributes. |
74 | However, the book and drawer related sysfs files will only be created if | |
75 | CONFIG_SCHED_BOOK and CONFIG_SCHED_DRAWER are selected, respectively. | |
a62247e1 | 76 | |
3a1c779f LB |
77 | CONFIG_SCHED_BOOK and CONFIG_SCHED_DRAWER are currently only used on s390, |
78 | where they reflect the cpu and cache hierarchy. | |
69dcc991 | 79 | |
c50cbb05 | 80 | For an architecture to support this feature, it must define some of |
e8cb6f1e MCC |
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 | |
54a53694 | 95 | topology_sibling_cpumask() which corresponds with thread_siblings). |
69dcc991 | 96 | |
c50cbb05 BH |
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: | |
e8cb6f1e | 100 | |
3a1c779f LB |
101 | 1) topology_physical_package_id: -1 |
102 | 2) topology_core_id: 0 | |
103 | 3) topology_sibling_cpumask: just the given CPU | |
104 | 4) topology_core_cpumask: just the given CPU | |
d62720ad | 105 | |
b40d8ed4 HC |
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(). | |
9bb0e9cb | 108 | For architectures that don't support drawers (CONFIG_SCHED_DRAWER) there are |
a62247e1 | 109 | no default definitions for topology_drawer_id() and topology_drawer_cpumask(). |
b40d8ed4 | 110 | |
663fb2fc | 111 | Additionally, CPU topology information is provided under |
d62720ad MT |
112 | /sys/devices/system/cpu and includes these files. The internal |
113 | source for the output is in brackets ("[]"). | |
114 | ||
e8cb6f1e | 115 | =========== ========================================================== |
663fb2fc | 116 | kernel_max: the maximum CPU index allowed by the kernel configuration. |
d62720ad MT |
117 | [NR_CPUS-1] |
118 | ||
663fb2fc | 119 | offline: CPUs that are not online because they have been |
d62720ad | 120 | HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit |
663fb2fc | 121 | of CPUs allowed by the kernel configuration (kernel_max |
d62720ad MT |
122 | above). [~cpu_online_mask + cpus >= NR_CPUS] |
123 | ||
663fb2fc | 124 | online: CPUs that are online and being scheduled [cpu_online_mask] |
d62720ad | 125 | |
663fb2fc | 126 | possible: CPUs that have been allocated resources and can be |
d62720ad MT |
127 | brought online if they are present. [cpu_possible_mask] |
128 | ||
663fb2fc | 129 | present: CPUs that have been identified as being present in the |
d62720ad | 130 | system. [cpu_present_mask] |
e8cb6f1e | 131 | =========== ========================================================== |
d62720ad MT |
132 | |
133 | The format for the above output is compatible with cpulist_parse() | |
134 | [see <linux/cpumask.h>]. Some examples follow. | |
135 | ||
663fb2fc | 136 | In this example, there are 64 CPUs in the system but cpus 32-63 exceed |
d62720ad | 137 | the kernel max which is limited to 0..31 by the NR_CPUS config option |
663fb2fc | 138 | being 32. Note also that CPUs 2 and 4-31 are not online but could be |
e8cb6f1e | 139 | brought online as they are both present and possible:: |
d62720ad MT |
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 | |
663fb2fc AC |
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 | |
e8cb6f1e | 150 | online.):: |
d62720ad MT |
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 | |
663fb2fc | 159 | as well as more information on the various cpumasks. |