-Export cpu topology info via 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,
drivers/base/topology.c, is to export the 4 attributes.
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
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 <linux/cpumask.h>]. 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.
+
+ kernel_max: 31
+ offline: 2,4-31,32-63
+ online: 0-1,3
+ possible: 0-31
+ present: 0-31
+
+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.)
+
+ 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.
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff