sched: report CPU usage in CFS cgroup directories

Adds a cpu.usage file to the CFS cgroup that reports CPU usage in
milliseconds for that cgroup's tasks

[ mingo@elte.hu: style cleanups. ]

Signed-off-by: Paul Menage <menage@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 33 insertions, 5 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 470480790f3f..6c4abfbd68e6 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7211,15 +7211,43 @@ static u64 cpu_shares_read_uint(struct cgroup *cgrp, struct cftype *cft)
         return (u64) tg->shares;
 }
 
-static struct cftype cpu_shares = {
-        .name = "shares",
-        .read_uint = cpu_shares_read_uint,
-        .write_uint = cpu_shares_write_uint,
+static u64 cpu_usage_read(struct cgroup *cgrp, struct cftype *cft)
+{
+        struct task_group *tg = cgroup_tg(cgrp);
+        unsigned long flags;
+        u64 res = 0;
+        int i;
+
+        for_each_possible_cpu(i) {
+                /*
+                 * Lock to prevent races with updating 64-bit counters
+                 * on 32-bit arches.
+                 */
+                spin_lock_irqsave(&cpu_rq(i)->lock, flags);
+                res += tg->se[i]->sum_exec_runtime;
+                spin_unlock_irqrestore(&cpu_rq(i)->lock, flags);
+        }
+        /* Convert from ns to ms */
+        do_div(res, 1000000);
+
+        return res;
+}
+
+static struct cftype cpu_files[] = {
+        {
+                .name = "shares",
+                .read_uint = cpu_shares_read_uint,
+                .write_uint = cpu_shares_write_uint,
+        },
+        {
+                .name = "usage",
+                .read_uint = cpu_usage_read,
+        },
 };
 
 static int cpu_cgroup_populate(struct cgroup_subsys *ss, struct cgroup *cont)
 {
-        return cgroup_add_file(cont, ss, &cpu_shares);
+        return cgroup_add_files(cont, ss, cpu_files, ARRAY_SIZE(cpu_files));
 }
 
 struct cgroup_subsys cpu_cgroup_subsys = {