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-rw-r--r--Documentation/cputopology.txt47
1 files changed, 30 insertions, 17 deletions
diff --git a/Documentation/cputopology.txt b/Documentation/cputopology.txt
index b41f3e58aefa..f1c5c4bccd3e 100644
--- a/Documentation/cputopology.txt
+++ b/Documentation/cputopology.txt
@@ -1,15 +1,28 @@
1 1
2Export cpu topology info via sysfs. Items (attributes) are similar 2Export CPU topology info via sysfs. Items (attributes) are similar
3to /proc/cpuinfo. 3to /proc/cpuinfo.
4 4
51) /sys/devices/system/cpu/cpuX/topology/physical_package_id: 51) /sys/devices/system/cpu/cpuX/topology/physical_package_id:
6represent the physical package id of cpu X; 6
7 physical package id of cpuX. Typically corresponds to a physical
8 socket number, but the actual value is architecture and platform
9 dependent.
10
72) /sys/devices/system/cpu/cpuX/topology/core_id: 112) /sys/devices/system/cpu/cpuX/topology/core_id:
8represent the cpu core id to cpu X; 12
13 the CPU core ID of cpuX. Typically it is the hardware platform's
14 identifier (rather than the kernel's). The actual value is
15 architecture and platform dependent.
16
93) /sys/devices/system/cpu/cpuX/topology/thread_siblings: 173) /sys/devices/system/cpu/cpuX/topology/thread_siblings:
10represent the thread siblings to cpu X in the same core; 18
19 internel kernel map of cpuX's hardware threads within the same
20 core as cpuX
21
114) /sys/devices/system/cpu/cpuX/topology/core_siblings: 224) /sys/devices/system/cpu/cpuX/topology/core_siblings:
12represent the thread siblings to cpu X in the same physical package; 23
24 internal kernel map of cpuX's hardware threads within the same
25 physical_package_id.
13 26
14To implement it in an architecture-neutral way, a new source file, 27To implement it in an architecture-neutral way, a new source file,
15drivers/base/topology.c, is to export the 4 attributes. 28drivers/base/topology.c, is to export the 4 attributes.
@@ -32,32 +45,32 @@ not defined by include/asm-XXX/topology.h:
323) thread_siblings: just the given CPU 453) thread_siblings: just the given CPU
334) core_siblings: just the given CPU 464) core_siblings: just the given CPU
34 47
35Additionally, cpu topology information is provided under 48Additionally, CPU topology information is provided under
36/sys/devices/system/cpu and includes these files. The internal 49/sys/devices/system/cpu and includes these files. The internal
37source for the output is in brackets ("[]"). 50source for the output is in brackets ("[]").
38 51
39 kernel_max: the maximum cpu index allowed by the kernel configuration. 52 kernel_max: the maximum CPU index allowed by the kernel configuration.
40 [NR_CPUS-1] 53 [NR_CPUS-1]
41 54
42 offline: cpus that are not online because they have been 55 offline: CPUs that are not online because they have been
43 HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit 56 HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit
44 of cpus allowed by the kernel configuration (kernel_max 57 of CPUs allowed by the kernel configuration (kernel_max
45 above). [~cpu_online_mask + cpus >= NR_CPUS] 58 above). [~cpu_online_mask + cpus >= NR_CPUS]
46 59
47 online: cpus that are online and being scheduled [cpu_online_mask] 60 online: CPUs that are online and being scheduled [cpu_online_mask]
48 61
49 possible: cpus that have been allocated resources and can be 62 possible: CPUs that have been allocated resources and can be
50 brought online if they are present. [cpu_possible_mask] 63 brought online if they are present. [cpu_possible_mask]
51 64
52 present: cpus that have been identified as being present in the 65 present: CPUs that have been identified as being present in the
53 system. [cpu_present_mask] 66 system. [cpu_present_mask]
54 67
55The format for the above output is compatible with cpulist_parse() 68The format for the above output is compatible with cpulist_parse()
56[see <linux/cpumask.h>]. Some examples follow. 69[see <linux/cpumask.h>]. Some examples follow.
57 70
58In this example, there are 64 cpus in the system but cpus 32-63 exceed 71In this example, there are 64 CPUs in the system but cpus 32-63 exceed
59the kernel max which is limited to 0..31 by the NR_CPUS config option 72the kernel max which is limited to 0..31 by the NR_CPUS config option
60being 32. Note also that cpus 2 and 4-31 are not online but could be 73being 32. Note also that CPUs 2 and 4-31 are not online but could be
61brought online as they are both present and possible. 74brought online as they are both present and possible.
62 75
63 kernel_max: 31 76 kernel_max: 31
@@ -67,8 +80,8 @@ brought online as they are both present and possible.
67 present: 0-31 80 present: 0-31
68 81
69In this example, the NR_CPUS config option is 128, but the kernel was 82In this example, the NR_CPUS config option is 128, but the kernel was
70started with possible_cpus=144. There are 4 cpus in the system and cpu2 83started with possible_cpus=144. There are 4 CPUs in the system and cpu2
71was manually taken offline (and is the only cpu that can be brought 84was manually taken offline (and is the only CPU that can be brought
72online.) 85online.)
73 86
74 kernel_max: 127 87 kernel_max: 127
@@ -78,4 +91,4 @@ online.)
78 present: 0-3 91 present: 0-3
79 92
80See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter 93See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter
81as well as more information on the various cpumask's. 94as well as more information on the various cpumasks.