2 files changed, 99 insertions, 6 deletions

diff --git a/Documentation/cgroups/cpuacct.txt b/Documentation/cgroups/cpuacct.txt
index bb775fbe43d7..8b930946c52a 100644
--- a/Documentation/cgroups/cpuacct.txt
+++ b/Documentation/cgroups/cpuacct.txt
@@ -30,3 +30,21 @@ 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.
+
+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+- It is possible to see slightly outdated values for user and system times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.
diff --git a/kernel/sched.c b/kernel/sched.c
index c8d7f17bd036..8d1bdbe8aafc 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1393,10 +1393,22 @@ iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
                    struct rq_iterator *iterator);
 #endif
 
+/* Time spent by the tasks of the cpu accounting group executing in ... */
+enum cpuacct_stat_index {
+        CPUACCT_STAT_USER,      /* ... user mode */
+        CPUACCT_STAT_SYSTEM,    /* ... kernel mode */
+
+        CPUACCT_STAT_NSTATS,
+};
+
 #ifdef CONFIG_CGROUP_CPUACCT
 static void cpuacct_charge(struct task_struct *tsk, u64 cputime);
+static void cpuacct_update_stats(struct task_struct *tsk,
+                enum cpuacct_stat_index idx, cputime_t val);
 #else
 static inline void cpuacct_charge(struct task_struct *tsk, u64 cputime) {}
+static inline void cpuacct_update_stats(struct task_struct *tsk,
+                enum cpuacct_stat_index idx, cputime_t val) {}
 #endif
 
 static inline void inc_cpu_load(struct rq *rq, unsigned long load)
@@ -4236,6 +4248,8 @@ void account_user_time(struct task_struct *p, cputime_t cputime,
                 cpustat->nice = cputime64_add(cpustat->nice, tmp);
         else
                 cpustat->user = cputime64_add(cpustat->user, tmp);
+
+        cpuacct_update_stats(p, CPUACCT_STAT_USER, cputime);
         /* Account for user time used */
         acct_update_integrals(p);
 }
@@ -4297,6 +4311,8 @@ void account_system_time(struct task_struct *p, int hardirq_offset,
         else
                 cpustat->system = cputime64_add(cpustat->system, tmp);
 
+        cpuacct_update_stats(p, CPUACCT_STAT_SYSTEM, cputime);
+
         /* Account for system time used */
         acct_update_integrals(p);
 }
@@ -9539,6 +9555,7 @@ struct cpuacct {
         struct cgroup_subsys_state css;
         /* cpuusage holds pointer to a u64-type object on every cpu */
         u64 *cpuusage;
+        struct percpu_counter cpustat[CPUACCT_STAT_NSTATS];
         struct cpuacct *parent;
 };
 
@@ -9563,20 +9580,32 @@ static struct cgroup_subsys_state *cpuacct_create(
         struct cgroup_subsys *ss, struct cgroup *cgrp)
 {
         struct cpuacct *ca = kzalloc(sizeof(*ca), GFP_KERNEL);
+        int i;
 
         if (!ca)
-                return ERR_PTR(-ENOMEM);
+                goto out;
 
         ca->cpuusage = alloc_percpu(u64);
-        if (!ca->cpuusage) {
-                kfree(ca);
-                return ERR_PTR(-ENOMEM);
-        }
+        if (!ca->cpuusage)
+                goto out_free_ca;
+
+        for (i = 0; i < CPUACCT_STAT_NSTATS; i++)
+                if (percpu_counter_init(&ca->cpustat[i], 0))
+                        goto out_free_counters;
 
         if (cgrp->parent)
                 ca->parent = cgroup_ca(cgrp->parent);
 
         return &ca->css;
+
+out_free_counters:
+        while (--i >= 0)
+                percpu_counter_destroy(&ca->cpustat[i]);
+        free_percpu(ca->cpuusage);
+out_free_ca:
+        kfree(ca);
+out:
+        return ERR_PTR(-ENOMEM);
 }
 
 /* destroy an existing cpu accounting group */
@@ -9584,7 +9613,10 @@ static void
 cpuacct_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
 {
         struct cpuacct *ca = cgroup_ca(cgrp);
+        int i;
 
+        for (i = 0; i < CPUACCT_STAT_NSTATS; i++)
+                percpu_counter_destroy(&ca->cpustat[i]);
         free_percpu(ca->cpuusage);
         kfree(ca);
 }
@@ -9671,6 +9703,25 @@ static int cpuacct_percpu_seq_read(struct cgroup *cgroup, struct cftype *cft,
         return 0;
 }
 
+static const char *cpuacct_stat_desc[] = {
+        [CPUACCT_STAT_USER] = "user",
+        [CPUACCT_STAT_SYSTEM] = "system",
+};
+
+static int cpuacct_stats_show(struct cgroup *cgrp, struct cftype *cft,
+                struct cgroup_map_cb *cb)
+{
+        struct cpuacct *ca = cgroup_ca(cgrp);
+        int i;
+
+        for (i = 0; i < CPUACCT_STAT_NSTATS; i++) {
+                s64 val = percpu_counter_read(&ca->cpustat[i]);
+                val = cputime64_to_clock_t(val);
+                cb->fill(cb, cpuacct_stat_desc[i], val);
+        }
+        return 0;
+}
+
 static struct cftype files[] = {
         {
                 .name = "usage",
@@ -9681,7 +9732,10 @@ static struct cftype files[] = {
                 .name = "usage_percpu",
                 .read_seq_string = cpuacct_percpu_seq_read,
         },
-
+        {
+                .name = "stat",
+                .read_map = cpuacct_stats_show,
+        },
 };
 
 static int cpuacct_populate(struct cgroup_subsys *ss, struct cgroup *cgrp)
@@ -9716,6 +9770,27 @@ static void cpuacct_charge(struct task_struct *tsk, u64 cputime)
         rcu_read_unlock();
 }
 
+/*
+ * Charge the system/user time to the task's accounting group.
+ */
+static void cpuacct_update_stats(struct task_struct *tsk,
+                enum cpuacct_stat_index idx, cputime_t val)
+{
+        struct cpuacct *ca;
+
+        if (unlikely(!cpuacct_subsys.active))
+                return;
+
+        rcu_read_lock();
+        ca = task_ca(tsk);
+
+        do {
+                percpu_counter_add(&ca->cpustat[idx], val);
+                ca = ca->parent;
+        } while (ca);
+        rcu_read_unlock();
+}
+
 struct cgroup_subsys cpuacct_subsys = {
         .name = "cpuacct",
         .create = cpuacct_create,