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authorBharata B Rao <bharata@linux.vnet.ibm.com>2008-11-10 10:11:13 -0500
committerIngo Molnar <mingo@elte.hu>2008-11-11 06:13:28 -0500
commit934352f214b3251eb0793c1209d346595a661d80 (patch)
tree375ac56485c20f7b7cf783c3ca2980a76dc94fce /Documentation/controllers
parentff9b48c3598732926fa09afd7f526981c32a48cc (diff)
sched: add hierarchical accounting to cpu accounting controller
Impact: improve CPU time accounting of tasks under the cpu accounting controller Add hierarchical accounting to cpu accounting controller and include cpuacct documentation. Currently, while charging the task's cputime to its accounting group, the accounting group hierarchy isn't updated. This patch charges the cputime of a task to its accounting group and all its parent accounting groups. Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Reviewed-by: Paul Menage <menage@google.com> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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1CPU Accounting Controller
2-------------------------
3
4The CPU accounting controller is used to group tasks using cgroups and
5account the CPU usage of these groups of tasks.
6
7The CPU accounting controller supports multi-hierarchy groups. An accounting
8group accumulates the CPU usage of all of its child groups and the tasks
9directly present in its group.
10
11Accounting groups can be created by first mounting the cgroup filesystem.
12
13# mkdir /cgroups
14# mount -t cgroup -ocpuacct none /cgroups
15
16With the above step, the initial or the parent accounting group
17becomes visible at /cgroups. At bootup, this group includes all the
18tasks in the system. /cgroups/tasks lists the tasks in this cgroup.
19/cgroups/cpuacct.usage gives the CPU time (in nanoseconds) obtained by
20this group which is essentially the CPU time obtained by all the tasks
21in the system.
22
23New accounting groups can be created under the parent group /cgroups.
24
25# cd /cgroups
26# mkdir g1
27# echo $$ > g1
28
29The above steps create a new group g1 and move the current shell
30process (bash) into it. CPU time consumed by this bash and its children
31can be obtained from g1/cpuacct.usage and the same is accumulated in
32/cgroups/cpuacct.usage also.