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Subject[patch 15/18] sched: add exports tracking cfs bandwidth control statistics
From: Nikhil Rao <ncrao@google.com>

This change introduces statistics exports for the cpu sub-system, these are
added through the use of a stat file similar to that exported by other
subsystems.

The following exports are included:

nr_periods: number of periods in which execution occurred
nr_throttled: the number of periods above in which execution was throttle
throttled_time: cumulative wall-time that any cpus have been throttled for
this group

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Nikhil Rao <ncrao@google.com>
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>

---
kernel/sched.c | 21 +++++++++++++++++++++
kernel/sched_fair.c | 7 +++++++
2 files changed, 28 insertions(+)

Index: tip/kernel/sched.c
===================================================================
--- tip.orig/kernel/sched.c
+++ tip/kernel/sched.c
@@ -259,6 +259,9 @@ struct cfs_bandwidth {
struct hrtimer period_timer;
struct list_head throttled_cfs_rq;

+ /* statistics */
+ int nr_periods, nr_throttled;
+ u64 throttled_time;
#endif
};

@@ -399,6 +402,7 @@ struct cfs_rq {
u64 runtime_expires;
s64 runtime_remaining;

+ u64 throttled_timestamp;
int throttled, throttle_count;
struct list_head throttled_list;
#endif
@@ -9213,6 +9217,19 @@ static int __cfs_schedulable(struct task

return ret;
}
+
+static int cpu_stats_show(struct cgroup *cgrp, struct cftype *cft,
+ struct cgroup_map_cb *cb)
+{
+ struct task_group *tg = cgroup_tg(cgrp);
+ struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
+
+ cb->fill(cb, "nr_periods", cfs_b->nr_periods);
+ cb->fill(cb, "nr_throttled", cfs_b->nr_throttled);
+ cb->fill(cb, "throttled_time", cfs_b->throttled_time);
+
+ return 0;
+}
#endif /* CONFIG_CFS_BANDWIDTH */
#endif /* CONFIG_FAIR_GROUP_SCHED */

@@ -9259,6 +9276,10 @@ static struct cftype cpu_files[] = {
.read_u64 = cpu_cfs_period_read_u64,
.write_u64 = cpu_cfs_period_write_u64,
},
+ {
+ .name = "stat",
+ .read_map = cpu_stats_show,
+ },
#endif
#ifdef CONFIG_RT_GROUP_SCHED
{
Index: tip/kernel/sched_fair.c
===================================================================
--- tip.orig/kernel/sched_fair.c
+++ tip/kernel/sched_fair.c
@@ -1528,6 +1528,7 @@ static void throttle_cfs_rq(struct cfs_r
rq->nr_running -= task_delta;

cfs_rq->throttled = 1;
+ cfs_rq->throttled_timestamp = rq->clock;
raw_spin_lock(&cfs_b->lock);
list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
raw_spin_unlock(&cfs_b->lock);
@@ -1545,8 +1546,10 @@ static void unthrottle_cfs_rq(struct cfs

cfs_rq->throttled = 0;
raw_spin_lock(&cfs_b->lock);
+ cfs_b->throttled_time += rq->clock - cfs_rq->throttled_timestamp;
list_del_rcu(&cfs_rq->throttled_list);
raw_spin_unlock(&cfs_b->lock);
+ cfs_rq->throttled_timestamp = 0;

update_rq_clock(rq);
/* update hierarchical throttle state */
@@ -1634,6 +1637,7 @@ static int do_sched_cfs_period_timer(str
throttled = !list_empty(&cfs_b->throttled_cfs_rq);
/* idle depends on !throttled (for the case of a large deficit) */
idle = cfs_b->idle && !throttled;
+ cfs_b->nr_periods += overrun;

/* if we're going inactive then everything else can be deferred */
if (idle)
@@ -1647,6 +1651,9 @@ static int do_sched_cfs_period_timer(str
goto out_unlock;
}

+ /* account preceding periods in which throttling occurred */
+ cfs_b->nr_throttled += overrun;
+
/*
* There are throttled entities so we must first use the new bandwidth
* to unthrottle them before making it generally available. This



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