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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>
This commit is contained in:
Bharata B Rao 2008-11-10 20:41:13 +05:30 committed by Ingo Molnar
parent ff9b48c359
commit 934352f214
2 changed files with 41 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
Documentation/controllers/cpuacct.txt Normal file
View File

@ -0,0 +1,32 @@
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.

12
kernel/sched.c
View File

@ -9196,11 +9196,12 @@ struct cgroup_subsys cpu_cgroup_subsys = {
* (balbir@in.ibm.com). * (balbir@in.ibm.com).
*/ */
/* track cpu usage of a group of tasks */ /* track cpu usage of a group of tasks and its child groups */
struct cpuacct { struct cpuacct {
struct cgroup_subsys_state css; struct cgroup_subsys_state css;
/* cpuusage holds pointer to a u64-type object on every cpu */ /* cpuusage holds pointer to a u64-type object on every cpu */
u64 *cpuusage; u64 *cpuusage;
struct cpuacct *parent;
}; };
struct cgroup_subsys cpuacct_subsys; struct cgroup_subsys cpuacct_subsys;
@ -9234,6 +9235,9 @@ static struct cgroup_subsys_state *cpuacct_create(
return ERR_PTR(-ENOMEM); return ERR_PTR(-ENOMEM);
} }
if (cgrp->parent)
ca->parent = cgroup_ca(cgrp->parent);
return &ca->css; return &ca->css;
} }
@ -9313,14 +9317,16 @@ static int cpuacct_populate(struct cgroup_subsys *ss, struct cgroup *cgrp)
static void cpuacct_charge(struct task_struct *tsk, u64 cputime) static void cpuacct_charge(struct task_struct *tsk, u64 cputime)
{ {
struct cpuacct *ca; struct cpuacct *ca;
int cpu;
if (!cpuacct_subsys.active) if (!cpuacct_subsys.active)
return; return;
cpu = task_cpu(tsk);
ca = task_ca(tsk); ca = task_ca(tsk);
if (ca) {
u64 *cpuusage = percpu_ptr(ca->cpuusage, task_cpu(tsk));
for (; ca; ca = ca->parent) {
u64 *cpuusage = percpu_ptr(ca->cpuusage, cpu);
*cpuusage += cputime; *cpuusage += cputime;
} }
} }