[deliverable/linux.git] / Documentation / controllers / cpuacct.txt

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.

# mkdir /cgroups
# mount -t cgroup -ocpuacct none /cgroups

With the above step, the initial or the parent accounting group
becomes visible at /cgroups. At bootup, this group includes all the
tasks in the system. /cgroups/tasks lists the tasks in this cgroup.
/cgroups/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 /cgroups.

# cd /cgroups
# mkdir g1
# echo $$ > g1

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
/cgroups/cpuacct.usage also.
Commit	Line	Data
934352f2 BR	1	CPU Accounting Controller
	2	-------------------------
	3
	4	The CPU accounting controller is used to group tasks using cgroups and
	5	account the CPU usage of these groups of tasks.
	6
	7	The CPU accounting controller supports multi-hierarchy groups. An accounting
	8	group accumulates the CPU usage of all of its child groups and the tasks
	9	directly present in its group.
	10
	11	Accounting groups can be created by first mounting the cgroup filesystem.
	12
	13	# mkdir /cgroups
	14	# mount -t cgroup -ocpuacct none /cgroups
	15
	16	With the above step, the initial or the parent accounting group
	17	becomes visible at /cgroups. At bootup, this group includes all the
	18	tasks in the system. /cgroups/tasks lists the tasks in this cgroup.
	19	/cgroups/cpuacct.usage gives the CPU time (in nanoseconds) obtained by
	20	this group which is essentially the CPU time obtained by all the tasks
	21	in the system.
	22
	23	New accounting groups can be created under the parent group /cgroups.
	24
	25	# cd /cgroups
	26	# mkdir g1
	27	# echo $$ > g1
	28
	29	The above steps create a new group g1 and move the current shell
	30	process (bash) into it. CPU time consumed by this bash and its children
	31	can be obtained from g1/cpuacct.usage and the same is accumulated in
	32	/cgroups/cpuacct.usage also.