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>

diff --git a/kernel/sched.c b/kernel/sched.c
index 4704807..6c4abfb 100644 (file)
--- 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 = {