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author | Mauro Carvalho Chehab | 2019-06-12 19:52:41 +0200 |
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committer | Tejun Heo | 2019-06-14 22:29:54 +0200 |
commit | 99c8b231ae6c6ca4ca2fd1c0b3701071f589661f (patch) | |
tree | 6b254a5077095477d9b6d38b70872290fb9f2560 /Documentation/cgroup-v1/cpuacct.rst | |
parent | cgroup: Move cgroup_parse_float() implementation out of CONFIG_SYSFS (diff) | |
download | kernel-qcow2-linux-99c8b231ae6c6ca4ca2fd1c0b3701071f589661f.tar.gz kernel-qcow2-linux-99c8b231ae6c6ca4ca2fd1c0b3701071f589661f.tar.xz kernel-qcow2-linux-99c8b231ae6c6ca4ca2fd1c0b3701071f589661f.zip |
docs: cgroup-v1: convert docs to ReST and rename to *.rst
Convert the cgroup-v1 files to ReST format, in order to
allow a later addition to the admin-guide.
The conversion is actually:
- add blank lines and identation in order to identify paragraphs;
- fix tables markups;
- add some lists markups;
- mark literal blocks;
- adjust title markups.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'Documentation/cgroup-v1/cpuacct.rst')
-rw-r--r-- | Documentation/cgroup-v1/cpuacct.rst | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/Documentation/cgroup-v1/cpuacct.rst b/Documentation/cgroup-v1/cpuacct.rst new file mode 100644 index 000000000000..d30ed81d2ad7 --- /dev/null +++ b/Documentation/cgroup-v1/cpuacct.rst @@ -0,0 +1,50 @@ +========================= +CPU Accounting Controller +========================= + +The CPU accounting controller is used to group tasks using cgroups and +account the CPU usage of these groups of tasks. + +The CPU accounting controller supports multi-hierarchy groups. An accounting +group accumulates the CPU usage of all of its child groups and the tasks +directly present in its group. + +Accounting groups can be created by first mounting the cgroup filesystem:: + + # mount -t cgroup -ocpuacct none /sys/fs/cgroup + +With the above step, the initial or the parent accounting group becomes +visible at /sys/fs/cgroup. At bootup, this group includes all the tasks in +the system. /sys/fs/cgroup/tasks lists the tasks in this cgroup. +/sys/fs/cgroup/cpuacct.usage gives the CPU time (in nanoseconds) obtained +by this group which is essentially the CPU time obtained by all the tasks +in the system. + +New accounting groups can be created under the parent group /sys/fs/cgroup:: + + # cd /sys/fs/cgroup + # mkdir g1 + # echo $$ > g1/tasks + +The above steps create a new group g1 and move the current shell +process (bash) into it. CPU time consumed by this bash and its children +can be obtained from g1/cpuacct.usage and the same is accumulated in +/sys/fs/cgroup/cpuacct.usage also. + +cpuacct.stat file lists a few statistics which further divide the +CPU time obtained by the cgroup into user and system times. Currently +the following statistics are supported: + +user: Time spent by tasks of the cgroup in user mode. +system: Time spent by tasks of the cgroup in kernel mode. + +user and system are in USER_HZ unit. + +cpuacct controller uses percpu_counter interface to collect user and +system times. This has two side effects: + +- It is theoretically possible to see wrong values for user and system times. + This is because percpu_counter_read() on 32bit systems isn't safe + against concurrent writes. +- It is possible to see slightly outdated values for user and system times + due to the batch processing nature of percpu_counter. |