mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-29 07:34:06 +08:00
54a5369487
The documentation on cpu topology seems to be a bit out-of-date. It doesn't mention the **_siblings_list attributes and uses old names for topology_**_cpumask() macros. Add information on missing attributes plus some additional clarifications. Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com> Cc: Benoit Cousson <bcousson@baylibre.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Jean Delvare <jdelvare@suse.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Drokin <oleg.drokin@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rafael J. Wysocki <rjw@rjwysocki.net> Cc: Russell King <linux@arm.linux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Viresh Kumar <viresh.kumar@linaro.org> Link: http://lkml.kernel.org/r/1432645896-12588-3-git-send-email-bgolaszewski@baylibre.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
129 lines
4.5 KiB
Plaintext
129 lines
4.5 KiB
Plaintext
|
|
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/thread_siblings:
|
|
|
|
internal kernel map of cpuX's hardware threads within the same
|
|
core as cpuX.
|
|
|
|
5) /sys/devices/system/cpu/cpuX/topology/thread_siblings_list:
|
|
|
|
human-readable list of cpuX's hardware threads within the same
|
|
core as cpuX.
|
|
|
|
6) /sys/devices/system/cpu/cpuX/topology/core_siblings:
|
|
|
|
internal kernel map of cpuX's hardware threads within the same
|
|
physical_package_id.
|
|
|
|
7) /sys/devices/system/cpu/cpuX/topology/core_siblings_list:
|
|
|
|
human-readable list of cpuX's hardware threads within the same
|
|
physical_package_id.
|
|
|
|
8) /sys/devices/system/cpu/cpuX/topology/book_siblings:
|
|
|
|
internal kernel map of cpuX's hardware threads within the same
|
|
book_id.
|
|
|
|
9) /sys/devices/system/cpu/cpuX/topology/book_siblings_list:
|
|
|
|
human-readable list of cpuX's hardware threads within the same
|
|
book_id.
|
|
|
|
To implement it in an architecture-neutral way, a new source file,
|
|
drivers/base/topology.c, is to export the 6 or 9 attributes. The three book
|
|
related sysfs files will only be created if CONFIG_SCHED_BOOK is selected.
|
|
|
|
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_sibling_cpumask(cpu)
|
|
#define topology_core_cpumask(cpu)
|
|
#define topology_book_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().
|
|
|
|
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.
|