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authorMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-06-27 14:56:51 -0300
committerMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-07-15 11:03:02 -0300
commit4f4cfa6c560c93ba180c30675cf845e1597de44c (patch)
tree0bbe2ec9e6ef62ed2a347504dda50c6bdbe43703 /Documentation/cputopology.txt
parentda82c92f1150f66afabf78d2c85ef9ac18dc6d38 (diff)
docs: admin-guide: add a series of orphaned documents
There are lots of documents that belong to the admin-guide but are on random places (most under Documentation root dir). Move them to the admin guide. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
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-===========================================
-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. They reside in
-/sys/devices/system/cpu/cpuX/topology/:
-
-physical_package_id:
-
- physical package id of cpuX. Typically corresponds to a physical
- socket number, but the actual value is architecture and platform
- dependent.
-
-die_id:
-
- the CPU die ID of cpuX. Typically it is the hardware platform's
- identifier (rather than the kernel's). The actual value is
- architecture and platform dependent.
-
-core_id:
-
- 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.
-
-book_id:
-
- the book ID of cpuX. Typically it is the hardware platform's
- identifier (rather than the kernel's). The actual value is
- architecture and platform dependent.
-
-drawer_id:
-
- the drawer ID of cpuX. Typically it is the hardware platform's
- identifier (rather than the kernel's). The actual value is
- architecture and platform dependent.
-
-core_cpus:
-
- internal kernel map of CPUs within the same core.
- (deprecated name: "thread_siblings")
-
-core_cpus_list:
-
- human-readable list of CPUs within the same core.
- (deprecated name: "thread_siblings_list");
-
-package_cpus:
-
- internal kernel map of the CPUs sharing the same physical_package_id.
- (deprecated name: "core_siblings")
-
-package_cpus_list:
-
- human-readable list of CPUs sharing the same physical_package_id.
- (deprecated name: "core_siblings_list")
-
-die_cpus:
-
- internal kernel map of CPUs within the same die.
-
-die_cpus_list:
-
- human-readable list of CPUs within the same die.
-
-book_siblings:
-
- internal kernel map of cpuX's hardware threads within the same
- book_id.
-
-book_siblings_list:
-
- human-readable list of cpuX's hardware threads within the same
- book_id.
-
-drawer_siblings:
-
- internal kernel map of cpuX's hardware threads within the same
- drawer_id.
-
-drawer_siblings_list:
-
- human-readable list of cpuX's hardware threads within the same
- drawer_id.
-
-Architecture-neutral, drivers/base/topology.c, exports these attributes.
-However, the book and drawer related sysfs files will only be created if
-CONFIG_SCHED_BOOK and CONFIG_SCHED_DRAWER are selected, respectively.
-
-CONFIG_SCHED_BOOK and CONFIG_SCHED_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_die_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_die_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) topology_physical_package_id: -1
-2) topology_die_id: -1
-3) topology_core_id: 0
-4) topology_sibling_cpumask: just the given CPU
-5) topology_core_cpumask: just the given CPU
-6) topology_die_cpumask: just the given CPU
-
-For architectures that don't support books (CONFIG_SCHED_BOOK) there are no
-default definitions for topology_book_id() and topology_book_cpumask().
-For architectures that don't support drawers (CONFIG_SCHED_DRAWER) there are
-no default definitions for topology_drawer_id() and topology_drawer_cpumask().
-
-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.