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authorMauro Carvalho Chehab <mchehab@s-opensource.com>2017-07-17 11:17:36 -0300
committerMauro Carvalho Chehab <mchehab@s-opensource.com>2017-07-17 11:17:36 -0300
commita3db9d60a118571e696b684a6e8c692a2b064941 (patch)
treeff7bae0f79b7a2ee0bce03de4f883550200c52a9 /Documentation/cputopology.txt
parentmedia: staging: cxd2099: Activate cxd2099 buffer mode (diff)
parentLinux v4.13-rc1 (diff)
downloadlinux-dev-a3db9d60a118571e696b684a6e8c692a2b064941.tar.xz
linux-dev-a3db9d60a118571e696b684a6e8c692a2b064941.zip
Merge tag 'v4.13-rc1' into patchwork
Linux v4.13-rc1 * tag 'v4.13-rc1': (11136 commits) Linux v4.13-rc1 random: reorder READ_ONCE() in get_random_uXX random: suppress spammy warnings about unseeded randomness replace incorrect strscpy use in FORTIFY_SOURCE kmod: throttle kmod thread limit kmod: add test driver to stress test the module loader MAINTAINERS: give kmod some maintainer love xtensa: use generic fb.h fault-inject: add /proc/<pid>/fail-nth fault-inject: simplify access check for fail-nth fault-inject: make fail-nth read/write interface symmetric fault-inject: parse as natural 1-based value for fail-nth write interface fault-inject: automatically detect the number base for fail-nth write interface kernel/watchdog.c: use better pr_fmt prefix MAINTAINERS: move the befs tree to kernel.org lib/atomic64_test.c: add a test that atomic64_inc_not_zero() returns an int mm: fix overflow check in expand_upwards() ubifs: Set double hash cookie also for RENAME_EXCHANGE ubifs: Massage assert in ubifs_xattr_set() wrt. init_xattrs ubifs: Don't leak kernel memory to the MTD ...
Diffstat (limited to 'Documentation/cputopology.txt')
-rw-r--r--Documentation/cputopology.txt37
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