Based on kernel version 2.6.30. Page generated on 2009-06-11 10:12 EST.
1 2 Export cpu topology info via sysfs. Items (attributes) are similar 3 to /proc/cpuinfo. 4 5 1) /sys/devices/system/cpu/cpuX/topology/physical_package_id: 6 represent the physical package id of cpu X; 7 2) /sys/devices/system/cpu/cpuX/topology/core_id: 8 represent the cpu core id to cpu X; 9 3) /sys/devices/system/cpu/cpuX/topology/thread_siblings: 10 represent the thread siblings to cpu X in the same core; 11 4) /sys/devices/system/cpu/cpuX/topology/core_siblings: 12 represent the thread siblings to cpu X in the same physical package; 13 14 To implement it in an architecture-neutral way, a new source file, 15 drivers/base/topology.c, is to export the 4 attributes. 16 17 For an architecture to support this feature, it must define some of 18 these macros in include/asm-XXX/topology.h: 19 #define topology_physical_package_id(cpu) 20 #define topology_core_id(cpu) 21 #define topology_thread_cpumask(cpu) 22 #define topology_core_cpumask(cpu) 23 24 The type of **_id is int. 25 The type of siblings is (const) struct cpumask *. 26 27 To be consistent on all architectures, include/linux/topology.h 28 provides default definitions for any of the above macros that are 29 not defined by include/asm-XXX/topology.h: 30 1) physical_package_id: -1 31 2) core_id: 0 32 3) thread_siblings: just the given CPU 33 4) core_siblings: just the given CPU 34 35 Additionally, cpu topology information is provided under 36 /sys/devices/system/cpu and includes these files. The internal 37 source for the output is in brackets ("[]"). 38 39 kernel_max: the maximum cpu index allowed by the kernel configuration. 40 [NR_CPUS-1] 41 42 offline: cpus that are not online because they have been 43 HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit 44 of cpus allowed by the kernel configuration (kernel_max 45 above). [~cpu_online_mask + cpus >= NR_CPUS] 46 47 online: cpus that are online and being scheduled [cpu_online_mask] 48 49 possible: cpus that have been allocated resources and can be 50 brought online if they are present. [cpu_possible_mask] 51 52 present: cpus that have been identified as being present in the 53 system. [cpu_present_mask] 54 55 The format for the above output is compatible with cpulist_parse() 56 [see <linux/cpumask.h>]. Some examples follow. 57 58 In this example, there are 64 cpus in the system but cpus 32-63 exceed 59 the kernel max which is limited to 0..31 by the NR_CPUS config option 60 being 32. Note also that cpus 2 and 4-31 are not online but could be 61 brought online as they are both present and possible. 62 63 kernel_max: 31 64 offline: 2,4-31,32-63 65 online: 0-1,3 66 possible: 0-31 67 present: 0-31 68 69 In this example, the NR_CPUS config option is 128, but the kernel was 70 started with possible_cpus=144. There are 4 cpus in the system and cpu2 71 was manually taken offline (and is the only cpu that can be brought 72 online.) 73 74 kernel_max: 127 75 offline: 2,4-127,128-143 76 online: 0-1,3 77 possible: 0-127 78 present: 0-3 79 80 See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter 81 as well as more information on the various cpumask's.
