diff options
| -rw-r--r-- | Documentation/cputopology.txt | 37 |
1 files changed, 22 insertions, 15 deletions
diff --git a/Documentation/cputopology.txt b/Documentation/cputopology.txt index 127c9d8c2174..c6e7e9196a8b 100644 --- a/Documentation/cputopology.txt +++ b/Documentation/cputopology.txt @@ -1,3 +1,6 @@ +=========================================== +How CPU topology info is exported via sysfs +=========================================== Export CPU topology info via sysfs. Items (attributes) are similar to /proc/cpuinfo output of some architectures: @@ -75,24 +78,26 @@ CONFIG_SCHED_BOOK and CONFIG_DRAWER are currently only used on s390, where they reflect the cpu and cache hierarchy. 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_book_id(cpu) -#define topology_drawer_id(cpu) -#define topology_sibling_cpumask(cpu) -#define topology_core_cpumask(cpu) -#define topology_book_cpumask(cpu) -#define topology_drawer_cpumask(cpu) - -The type of **_id macros is int. -The type of **_cpumask macros is (const) struct cpumask *. The latter -correspond with appropriate **_siblings sysfs attributes (except for +these macros in include/asm-XXX/topology.h:: + + #define topology_physical_package_id(cpu) + #define topology_core_id(cpu) + #define topology_book_id(cpu) + #define topology_drawer_id(cpu) + #define topology_sibling_cpumask(cpu) + #define topology_core_cpumask(cpu) + #define topology_book_cpumask(cpu) + #define topology_drawer_cpumask(cpu) + +The type of ``**_id macros`` is int. +The type of ``**_cpumask macros`` is ``(const) struct cpumask *``. The latter +correspond with appropriate ``**_siblings`` sysfs attributes (except for topology_sibling_cpumask() which corresponds with thread_siblings). 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) sibling_cpumask: just the given CPU @@ -107,6 +112,7 @@ 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] @@ -122,6 +128,7 @@ source for the output is in brackets ("[]"). 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. @@ -129,7 +136,7 @@ The format for the above output is compatible with cpulist_parse() 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. +brought online as they are both present and possible:: kernel_max: 31 offline: 2,4-31,32-63 @@ -140,7 +147,7 @@ brought online as they are both present and possible. 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.) +online.):: kernel_max: 127 offline: 2,4-127,128-143 |