Commit | Line | Data |
---|---|---|
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 | ||
0e344d8c LB |
15 | die_id: |
16 | ||
17 | the CPU die 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 | core_id: |
663fb2fc AC |
22 | |
23 | the CPU core 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 | book_id: |
b40d8ed4 HC |
28 | |
29 | the book 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 | drawer_id: |
a62247e1 HC |
34 | |
35 | the drawer ID of cpuX. Typically it is the hardware platform's | |
36 | identifier (rather than the kernel's). The actual value is | |
37 | architecture and platform dependent. | |
38 | ||
2e4c54da | 39 | core_cpus: |
663fb2fc | 40 | |
2e4c54da LB |
41 | internal kernel map of CPUs within the same core. |
42 | (deprecated name: "thread_siblings") | |
663fb2fc | 43 | |
2e4c54da | 44 | core_cpus_list: |
54a53694 | 45 | |
2e4c54da LB |
46 | human-readable list of CPUs within the same core. |
47 | (deprecated name: "thread_siblings_list"); | |
54a53694 | 48 | |
b73ed8dc | 49 | package_cpus: |
663fb2fc | 50 | |
b73ed8dc LB |
51 | internal kernel map of the CPUs sharing the same physical_package_id. |
52 | (deprecated name: "core_siblings") | |
69dcc991 | 53 | |
b73ed8dc | 54 | package_cpus_list: |
54a53694 | 55 | |
b73ed8dc LB |
56 | human-readable list of CPUs sharing the same physical_package_id. |
57 | (deprecated name: "core_siblings_list") | |
54a53694 | 58 | |
2e4c54da LB |
59 | die_cpus: |
60 | ||
61 | internal kernel map of CPUs within the same die. | |
62 | ||
63 | die_cpus_list: | |
64 | ||
65 | human-readable list of CPUs within the same die. | |
66 | ||
3a1c779f | 67 | book_siblings: |
b40d8ed4 HC |
68 | |
69 | internal kernel map of cpuX's hardware threads within the same | |
70 | book_id. | |
71 | ||
3a1c779f | 72 | book_siblings_list: |
54a53694 BG |
73 | |
74 | human-readable list of cpuX's hardware threads within the same | |
75 | book_id. | |
76 | ||
3a1c779f | 77 | drawer_siblings: |
a62247e1 HC |
78 | |
79 | internal kernel map of cpuX's hardware threads within the same | |
80 | drawer_id. | |
81 | ||
3a1c779f | 82 | drawer_siblings_list: |
a62247e1 HC |
83 | |
84 | human-readable list of cpuX's hardware threads within the same | |
85 | drawer_id. | |
86 | ||
3a1c779f LB |
87 | Architecture-neutral, drivers/base/topology.c, exports these attributes. |
88 | However, the book and drawer related sysfs files will only be created if | |
89 | CONFIG_SCHED_BOOK and CONFIG_SCHED_DRAWER are selected, respectively. | |
a62247e1 | 90 | |
3a1c779f LB |
91 | CONFIG_SCHED_BOOK and CONFIG_SCHED_DRAWER are currently only used on s390, |
92 | where they reflect the cpu and cache hierarchy. | |
69dcc991 | 93 | |
c50cbb05 | 94 | For an architecture to support this feature, it must define some of |
e8cb6f1e MCC |
95 | these macros in include/asm-XXX/topology.h:: |
96 | ||
97 | #define topology_physical_package_id(cpu) | |
0e344d8c | 98 | #define topology_die_id(cpu) |
e8cb6f1e MCC |
99 | #define topology_core_id(cpu) |
100 | #define topology_book_id(cpu) | |
101 | #define topology_drawer_id(cpu) | |
102 | #define topology_sibling_cpumask(cpu) | |
103 | #define topology_core_cpumask(cpu) | |
2e4c54da | 104 | #define topology_die_cpumask(cpu) |
e8cb6f1e MCC |
105 | #define topology_book_cpumask(cpu) |
106 | #define topology_drawer_cpumask(cpu) | |
107 | ||
108 | The type of ``**_id macros`` is int. | |
109 | The type of ``**_cpumask macros`` is ``(const) struct cpumask *``. The latter | |
110 | correspond with appropriate ``**_siblings`` sysfs attributes (except for | |
54a53694 | 111 | topology_sibling_cpumask() which corresponds with thread_siblings). |
69dcc991 | 112 | |
c50cbb05 BH |
113 | To be consistent on all architectures, include/linux/topology.h |
114 | provides default definitions for any of the above macros that are | |
115 | not defined by include/asm-XXX/topology.h: | |
e8cb6f1e | 116 | |
3a1c779f | 117 | 1) topology_physical_package_id: -1 |
0e344d8c LB |
118 | 2) topology_die_id: -1 |
119 | 3) topology_core_id: 0 | |
120 | 4) topology_sibling_cpumask: just the given CPU | |
121 | 5) topology_core_cpumask: just the given CPU | |
122 | 6) topology_die_cpumask: just the given CPU | |
d62720ad | 123 | |
b40d8ed4 HC |
124 | For architectures that don't support books (CONFIG_SCHED_BOOK) there are no |
125 | default definitions for topology_book_id() and topology_book_cpumask(). | |
9bb0e9cb | 126 | For architectures that don't support drawers (CONFIG_SCHED_DRAWER) there are |
a62247e1 | 127 | no default definitions for topology_drawer_id() and topology_drawer_cpumask(). |
b40d8ed4 | 128 | |
663fb2fc | 129 | Additionally, CPU topology information is provided under |
d62720ad MT |
130 | /sys/devices/system/cpu and includes these files. The internal |
131 | source for the output is in brackets ("[]"). | |
132 | ||
e8cb6f1e | 133 | =========== ========================================================== |
663fb2fc | 134 | kernel_max: the maximum CPU index allowed by the kernel configuration. |
d62720ad MT |
135 | [NR_CPUS-1] |
136 | ||
663fb2fc | 137 | offline: CPUs that are not online because they have been |
d62720ad | 138 | HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit |
663fb2fc | 139 | of CPUs allowed by the kernel configuration (kernel_max |
d62720ad MT |
140 | above). [~cpu_online_mask + cpus >= NR_CPUS] |
141 | ||
663fb2fc | 142 | online: CPUs that are online and being scheduled [cpu_online_mask] |
d62720ad | 143 | |
663fb2fc | 144 | possible: CPUs that have been allocated resources and can be |
d62720ad MT |
145 | brought online if they are present. [cpu_possible_mask] |
146 | ||
663fb2fc | 147 | present: CPUs that have been identified as being present in the |
d62720ad | 148 | system. [cpu_present_mask] |
e8cb6f1e | 149 | =========== ========================================================== |
d62720ad MT |
150 | |
151 | The format for the above output is compatible with cpulist_parse() | |
152 | [see <linux/cpumask.h>]. Some examples follow. | |
153 | ||
663fb2fc | 154 | In this example, there are 64 CPUs in the system but cpus 32-63 exceed |
d62720ad | 155 | the kernel max which is limited to 0..31 by the NR_CPUS config option |
663fb2fc | 156 | being 32. Note also that CPUs 2 and 4-31 are not online but could be |
e8cb6f1e | 157 | brought online as they are both present and possible:: |
d62720ad MT |
158 | |
159 | kernel_max: 31 | |
160 | offline: 2,4-31,32-63 | |
161 | online: 0-1,3 | |
162 | possible: 0-31 | |
163 | present: 0-31 | |
164 | ||
165 | In this example, the NR_CPUS config option is 128, but the kernel was | |
663fb2fc AC |
166 | started with possible_cpus=144. There are 4 CPUs in the system and cpu2 |
167 | was manually taken offline (and is the only CPU that can be brought | |
e8cb6f1e | 168 | online.):: |
d62720ad MT |
169 | |
170 | kernel_max: 127 | |
171 | offline: 2,4-127,128-143 | |
172 | online: 0-1,3 | |
173 | possible: 0-127 | |
174 | present: 0-3 | |
175 | ||
176 | See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter | |
663fb2fc | 177 | as well as more information on the various cpumasks. |