blob: 902d3151f527919ab190d8f30ff9253e3da2c8d0 [file] [log] [blame]
Zhang, Yanmin69dcc992006-02-03 03:04:36 -08001
Alex Chiang663fb2f2009-10-21 21:45:31 -06002Export CPU topology info via sysfs. Items (attributes) are similar
Zhang, Yanmin69dcc992006-02-03 03:04:36 -08003to /proc/cpuinfo.
4
51) /sys/devices/system/cpu/cpuX/topology/physical_package_id:
Alex Chiang663fb2f2009-10-21 21:45:31 -06006
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
Zhang, Yanmin69dcc992006-02-03 03:04:36 -0800112) /sys/devices/system/cpu/cpuX/topology/core_id:
Alex Chiang663fb2f2009-10-21 21:45:31 -060012
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
Heiko Carstensb40d8ed2010-08-31 10:28:17 +0200173) /sys/devices/system/cpu/cpuX/topology/book_id:
18
19 the book ID of cpuX. Typically it is the hardware platform's
20 identifier (rather than the kernel's). The actual value is
21 architecture and platform dependent.
22
234) /sys/devices/system/cpu/cpuX/topology/thread_siblings:
Alex Chiang663fb2f2009-10-21 21:45:31 -060024
25 internel kernel map of cpuX's hardware threads within the same
26 core as cpuX
27
Heiko Carstensb40d8ed2010-08-31 10:28:17 +0200285) /sys/devices/system/cpu/cpuX/topology/core_siblings:
Alex Chiang663fb2f2009-10-21 21:45:31 -060029
30 internal kernel map of cpuX's hardware threads within the same
31 physical_package_id.
Zhang, Yanmin69dcc992006-02-03 03:04:36 -080032
Heiko Carstensb40d8ed2010-08-31 10:28:17 +0200336) /sys/devices/system/cpu/cpuX/topology/book_siblings:
34
35 internal kernel map of cpuX's hardware threads within the same
36 book_id.
37
Zhang, Yanmin69dcc992006-02-03 03:04:36 -080038To implement it in an architecture-neutral way, a new source file,
Heiko Carstensb40d8ed2010-08-31 10:28:17 +020039drivers/base/topology.c, is to export the 4 or 6 attributes. The two book
40related sysfs files will only be created if CONFIG_SCHED_BOOK is selected.
Zhang, Yanmin69dcc992006-02-03 03:04:36 -080041
Ben Hutchingsc50cbb02008-06-04 21:47:29 -070042For an architecture to support this feature, it must define some of
43these macros in include/asm-XXX/topology.h:
Zhang, Yanmin69dcc992006-02-03 03:04:36 -080044#define topology_physical_package_id(cpu)
45#define topology_core_id(cpu)
Heiko Carstensb40d8ed2010-08-31 10:28:17 +020046#define topology_book_id(cpu)
Rusty Russellfbd59a82009-01-10 21:58:08 -080047#define topology_thread_cpumask(cpu)
48#define topology_core_cpumask(cpu)
Heiko Carstensb40d8ed2010-08-31 10:28:17 +020049#define topology_book_cpumask(cpu)
Zhang, Yanmin69dcc992006-02-03 03:04:36 -080050
51The type of **_id is int.
Rusty Russellfbd59a82009-01-10 21:58:08 -080052The type of siblings is (const) struct cpumask *.
Zhang, Yanmin69dcc992006-02-03 03:04:36 -080053
Ben Hutchingsc50cbb02008-06-04 21:47:29 -070054To be consistent on all architectures, include/linux/topology.h
55provides default definitions for any of the above macros that are
56not defined by include/asm-XXX/topology.h:
571) physical_package_id: -1
582) core_id: 0
593) thread_siblings: just the given CPU
604) core_siblings: just the given CPU
Mike Travisd62720a2008-12-17 14:14:30 -080061
Heiko Carstensb40d8ed2010-08-31 10:28:17 +020062For architectures that don't support books (CONFIG_SCHED_BOOK) there are no
63default definitions for topology_book_id() and topology_book_cpumask().
64
Alex Chiang663fb2f2009-10-21 21:45:31 -060065Additionally, CPU topology information is provided under
Mike Travisd62720a2008-12-17 14:14:30 -080066/sys/devices/system/cpu and includes these files. The internal
67source for the output is in brackets ("[]").
68
Alex Chiang663fb2f2009-10-21 21:45:31 -060069 kernel_max: the maximum CPU index allowed by the kernel configuration.
Mike Travisd62720a2008-12-17 14:14:30 -080070 [NR_CPUS-1]
71
Alex Chiang663fb2f2009-10-21 21:45:31 -060072 offline: CPUs that are not online because they have been
Mike Travisd62720a2008-12-17 14:14:30 -080073 HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit
Alex Chiang663fb2f2009-10-21 21:45:31 -060074 of CPUs allowed by the kernel configuration (kernel_max
Mike Travisd62720a2008-12-17 14:14:30 -080075 above). [~cpu_online_mask + cpus >= NR_CPUS]
76
Alex Chiang663fb2f2009-10-21 21:45:31 -060077 online: CPUs that are online and being scheduled [cpu_online_mask]
Mike Travisd62720a2008-12-17 14:14:30 -080078
Alex Chiang663fb2f2009-10-21 21:45:31 -060079 possible: CPUs that have been allocated resources and can be
Mike Travisd62720a2008-12-17 14:14:30 -080080 brought online if they are present. [cpu_possible_mask]
81
Alex Chiang663fb2f2009-10-21 21:45:31 -060082 present: CPUs that have been identified as being present in the
Mike Travisd62720a2008-12-17 14:14:30 -080083 system. [cpu_present_mask]
84
85The format for the above output is compatible with cpulist_parse()
86[see <linux/cpumask.h>]. Some examples follow.
87
Alex Chiang663fb2f2009-10-21 21:45:31 -060088In this example, there are 64 CPUs in the system but cpus 32-63 exceed
Mike Travisd62720a2008-12-17 14:14:30 -080089the kernel max which is limited to 0..31 by the NR_CPUS config option
Alex Chiang663fb2f2009-10-21 21:45:31 -060090being 32. Note also that CPUs 2 and 4-31 are not online but could be
Mike Travisd62720a2008-12-17 14:14:30 -080091brought online as they are both present and possible.
92
93 kernel_max: 31
94 offline: 2,4-31,32-63
95 online: 0-1,3
96 possible: 0-31
97 present: 0-31
98
99In this example, the NR_CPUS config option is 128, but the kernel was
Alex Chiang663fb2f2009-10-21 21:45:31 -0600100started with possible_cpus=144. There are 4 CPUs in the system and cpu2
101was manually taken offline (and is the only CPU that can be brought
Mike Travisd62720a2008-12-17 14:14:30 -0800102online.)
103
104 kernel_max: 127
105 offline: 2,4-127,128-143
106 online: 0-1,3
107 possible: 0-127
108 present: 0-3
109
110See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter
Alex Chiang663fb2f2009-10-21 21:45:31 -0600111as well as more information on the various cpumasks.