mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-16 01:04:08 +08:00
e8cb6f1edc
Each text file under Documentation follows a different format. Some doesn't even have titles! Change its representation to follow the adopted standard, using ReST markups for it to be parseable by Sphinx: - Add a title for the document; - mark literals; - use table markup for existing table. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
160 lines
5.6 KiB
Plaintext
160 lines
5.6 KiB
Plaintext
===========================================
|
|
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:
|
|
|
|
1) /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.
|
|
|
|
2) /sys/devices/system/cpu/cpuX/topology/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.
|
|
|
|
3) /sys/devices/system/cpu/cpuX/topology/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.
|
|
|
|
4) /sys/devices/system/cpu/cpuX/topology/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.
|
|
|
|
5) /sys/devices/system/cpu/cpuX/topology/thread_siblings:
|
|
|
|
internal kernel map of cpuX's hardware threads within the same
|
|
core as cpuX.
|
|
|
|
6) /sys/devices/system/cpu/cpuX/topology/thread_siblings_list:
|
|
|
|
human-readable list of cpuX's hardware threads within the same
|
|
core as cpuX.
|
|
|
|
7) /sys/devices/system/cpu/cpuX/topology/core_siblings:
|
|
|
|
internal kernel map of cpuX's hardware threads within the same
|
|
physical_package_id.
|
|
|
|
8) /sys/devices/system/cpu/cpuX/topology/core_siblings_list:
|
|
|
|
human-readable list of cpuX's hardware threads within the same
|
|
physical_package_id.
|
|
|
|
9) /sys/devices/system/cpu/cpuX/topology/book_siblings:
|
|
|
|
internal kernel map of cpuX's hardware threads within the same
|
|
book_id.
|
|
|
|
10) /sys/devices/system/cpu/cpuX/topology/book_siblings_list:
|
|
|
|
human-readable list of cpuX's hardware threads within the same
|
|
book_id.
|
|
|
|
11) /sys/devices/system/cpu/cpuX/topology/drawer_siblings:
|
|
|
|
internal kernel map of cpuX's hardware threads within the same
|
|
drawer_id.
|
|
|
|
12) /sys/devices/system/cpu/cpuX/topology/drawer_siblings_list:
|
|
|
|
human-readable list of cpuX's hardware threads within the same
|
|
drawer_id.
|
|
|
|
To implement it in an architecture-neutral way, a new source file,
|
|
drivers/base/topology.c, is to export the 6 to 12 attributes. The book
|
|
and drawer related sysfs files will only be created if CONFIG_SCHED_BOOK
|
|
and CONFIG_SCHED_DRAWER are selected.
|
|
|
|
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
|
|
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
|
|
4) core_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.
|