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Commit 934352f2 authored by Bharata B Rao's avatar Bharata B Rao Committed by Ingo Molnar
Browse files

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: default avatarSrivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: default avatarBharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: default avatarPaul Menage <menage@google.com>
Acked-by: default avatarBalbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent ff9b48c3

Documentation/controllers/cpuacct.txt

0 → 100644
+32 −0
Original line number Diff line number Diff line 
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.

kernel/sched.c

+9 −3
Original line number Diff line number Diff line
@@ -9196,11 +9196,12 @@ struct cgroup_subsys cpu_cgroup_subsys = { 
 * (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 cgroup_subsys_state css;

	/* cpuusage holds pointer to a u64-type object on every cpu */

	u64 *cpuusage;

	struct cpuacct *parent;

};



struct cgroup_subsys cpuacct_subsys;
@@ -9234,6 +9235,9 @@ static struct cgroup_subsys_state *cpuacct_create( 
		return ERR_PTR(-ENOMEM);

	}



	if (cgrp->parent)

		ca->parent = cgroup_ca(cgrp->parent);



	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)

{

	struct cpuacct *ca;

	int cpu;



	if (!cpuacct_subsys.active)

		return;



	cpu = task_cpu(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;

	}

}