X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=Documentation%2Fcputopology.txt;h=f1c5c4bccd3e8ed6674903eedbc59db3cf76ff9e;hb=ccbd6a5a4f76e821ed36f69fdaf59817c3a7f18e;hp=ff280e2e1613e808e4d7844376134dfa2bb1fc21;hpb=69dcc99199fe29b0a29471a3488d39d9d33b25fc;p=safe%2Fjmp%2Flinux-2.6 diff --git a/Documentation/cputopology.txt b/Documentation/cputopology.txt index ff280e2..f1c5c4b 100644 --- a/Documentation/cputopology.txt +++ b/Documentation/cputopology.txt @@ -1,41 +1,94 @@ -Export cpu topology info by sysfs. Items (attributes) are similar +Export CPU topology info via sysfs. Items (attributes) are similar to /proc/cpuinfo. 1) /sys/devices/system/cpu/cpuX/topology/physical_package_id: -represent the physical package id of cpu X; + + physical package id of cpuX. Typically corresponds to a physical + socket number, but the actual value is architecture and platform + dependent. + 2) /sys/devices/system/cpu/cpuX/topology/core_id: -represent the cpu core id to cpu X; + + the CPU core ID of cpuX. Typically it is the hardware platform's + identifier (rather than the kernel's). The actual value is + architecture and platform dependent. + 3) /sys/devices/system/cpu/cpuX/topology/thread_siblings: -represent the thread siblings to cpu X in the same core; + + internel kernel map of cpuX's hardware threads within the same + core as cpuX + 4) /sys/devices/system/cpu/cpuX/topology/core_siblings: -represent the thread siblings to cpu X in the same physical package; + + internal kernel map of cpuX's hardware threads within the same + physical_package_id. To implement it in an architecture-neutral way, a new source file, -driver/base/topology.c, is to export the 5 attributes. +drivers/base/topology.c, is to export the 4 attributes. -If one architecture wants to support this feature, it just needs to -implement 4 defines, typically in file include/asm-XXX/topology.h. -The 4 defines are: +For an architecture to support this feature, it must define some of +these macros in include/asm-XXX/topology.h: #define topology_physical_package_id(cpu) #define topology_core_id(cpu) -#define topology_thread_siblings(cpu) -#define topology_core_siblings(cpu) +#define topology_thread_cpumask(cpu) +#define topology_core_cpumask(cpu) The type of **_id is int. -The type of siblings is cpumask_t. +The type of siblings is (const) struct cpumask *. + +To be consistent on all architectures, include/linux/topology.h +provides default definitions for any of the above macros that are +not defined by include/asm-XXX/topology.h: +1) physical_package_id: -1 +2) core_id: 0 +3) thread_siblings: just the given CPU +4) core_siblings: just the given CPU + +Additionally, CPU topology information is provided under +/sys/devices/system/cpu and includes these files. The internal +source for the output is in brackets ("[]"). + + kernel_max: the maximum CPU index allowed by the kernel configuration. + [NR_CPUS-1] + + offline: CPUs that are not online because they have been + HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit + of CPUs allowed by the kernel configuration (kernel_max + above). [~cpu_online_mask + cpus >= NR_CPUS] + + online: CPUs that are online and being scheduled [cpu_online_mask] + + possible: CPUs that have been allocated resources and can be + brought online if they are present. [cpu_possible_mask] + + present: CPUs that have been identified as being present in the + system. [cpu_present_mask] + +The format for the above output is compatible with cpulist_parse() +[see ]. Some examples follow. + +In this example, there are 64 CPUs in the system but cpus 32-63 exceed +the kernel max which is limited to 0..31 by the NR_CPUS config option +being 32. Note also that CPUs 2 and 4-31 are not online but could be +brought online as they are both present and possible. -To be consistent on all architectures, the 4 attributes should have -deafult values if their values are unavailable. Below is the rule. -1) physical_package_id: If cpu has no physical package id, -1 is the -default value. -2) core_id: If cpu doesn't support multi-core, its core id is 0. -3) thread_siblings: Just include itself, if the cpu doesn't support -HT/multi-thread. -4) core_siblings: Just include itself, if the cpu doesn't support -multi-core and HT/Multi-thread. + kernel_max: 31 + offline: 2,4-31,32-63 + online: 0-1,3 + possible: 0-31 + present: 0-31 -So be careful when declaring the 4 defines in include/asm-XXX/topology.h. +In this example, the NR_CPUS config option is 128, but the kernel was +started with possible_cpus=144. There are 4 CPUs in the system and cpu2 +was manually taken offline (and is the only CPU that can be brought +online.) -If an attribute isn't defined on an architecture, it won't be exported. + kernel_max: 127 + offline: 2,4-127,128-143 + online: 0-1,3 + possible: 0-127 + present: 0-3 +See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter +as well as more information on the various cpumasks.