[PATCH 3/3] sched/fair: add tracepoints for cfs throttle

[Cong Wang]

This patch introduces two sched tracepoints to track
CFS throttle and unthrottle. The use case is to measure
how long each throttle is and to track when a CPU cgroup
is throttled and unthrottled.

Sample output:

     cfs-722   [000] dN.3    51.477702: sched_cfs_throttle: path=/test cpu=0 runtime_remaining=0
  <idle>-0     [000] d.h4    51.536659: sched_cfs_unthrottle: path=/test cpu=0 runtime_remaining=1

Cc: Paul Turner <pjt@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
---
 include/trace/events/sched.h | 42 ++++++++++++++++++++++++++++++++++++++++++
 kernel/sched/fair.c          |  2 ++
 2 files changed, 44 insertions(+)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index bc01e06bc716..3d9e00972e92 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -570,6 +570,48 @@ TRACE_EVENT(sched_wake_idle_without_ipi,
 
 	TP_printk("cpu=%d", __entry->cpu)
 );
+
+#ifdef CONFIG_CFS_BANDWIDTH
+DECLARE_EVENT_CLASS(sched_fair,
+
+	TP_PROTO(struct cfs_rq *cfs_rq),
+
+	TP_ARGS(cfs_rq),
+
+	TP_STRUCT__entry(
+		__field(	s64,		runtime_remaining	)
+		__field(	int,		cpu			)
+		__dynamic_array(char,		cfs_path,
+				cgroup_path(cfs_rq->tg->css.cgroup, NULL, 0) + 1)
+	),
+
+	TP_fast_assign(
+		__entry->runtime_remaining = cfs_rq->runtime_remaining;
+		__entry->cpu = cpu_of(cfs_rq->rq);
+		cgroup_path(cfs_rq->tg->css.cgroup,
+			    __get_dynamic_array(cfs_path),
+			    __get_dynamic_array_len(cfs_path));
+	),
+
+	TP_printk("path=%s cpu=%d runtime_remaining=%lld", __get_str(cfs_path),
+		  __entry->cpu, __entry->runtime_remaining)
+);
+
+DEFINE_EVENT(sched_fair, sched_cfs_throttle,
+
+	TP_PROTO(struct cfs_rq *cfs_rq),
+
+	TP_ARGS(cfs_rq)
+);
+
+DEFINE_EVENT(sched_fair, sched_cfs_unthrottle,
+
+	TP_PROTO(struct cfs_rq *cfs_rq),
+
+	TP_ARGS(cfs_rq)
+);
+#endif /* CONFIG_CFS_BANDWIDTH */
+
 #endif /* _TRACE_SCHED_H */
 
 /* This part must be outside protection */
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8a13ee006f39..3bcc40f2f272 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4736,6 +4736,7 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
 
 	cfs_rq->throttled = 1;
 	cfs_rq->throttled_clock = rq_clock(rq);
+	trace_sched_cfs_throttle(cfs_rq);
 	raw_spin_lock(&cfs_b->lock);
 	empty = list_empty(&cfs_b->throttled_cfs_rq);
 
@@ -4766,6 +4767,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 	se = cfs_rq->tg->se[cpu_of(rq)];
 
 	cfs_rq->throttled = 0;
+	trace_sched_cfs_unthrottle(cfs_rq);
 
 	update_rq_clock(rq);
 
-- 
2.13.0