[PATCH 4/4] sched: add trace event for idle injection

[Jacob Pan <jacob.jun.pan@linux.intel.com>]

Trace events for idle injection can be used to determine
timer activities for checking synchronization. In addition they
also helps to determine when the runqueue is throttled.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 include/linux/sched.h        |  5 +++++
 include/trace/events/sched.h | 25 +++++++++++++++++++++++++
 kernel/sched/fair.c          |  3 +++
 3 files changed, 33 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index ff551a3..99c79bf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -3189,6 +3189,11 @@ extern int proc_sched_cfs_idle_inject_duration_handler(struct ctl_table *table,
 						int write,
 						void __user *buffer,
 						size_t *length, loff_t *ppos);
+enum cfs_idle_inject_action {
+	CFS_IDLE_INJECT_TIMER,    /* timer sync point */
+	CFS_IDLE_INJECT_FORCED,   /* idle forced in rq */
+	CFS_IDLE_INJECT_YIELD_SOFTIRQ   /* yield to pending softirq */
+};
 #endif
 
 #endif
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 539d6bc..52c11c1 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -566,6 +566,31 @@ TRACE_EVENT(sched_wake_idle_without_ipi,
 
 	TP_printk("cpu=%d", __entry->cpu)
 );
+
+#ifdef CONFIG_CFS_IDLE_INJECT
+/*
+ * Tracepoint for idle injection
+ */
+TRACE_EVENT(sched_cfs_idle_inject,
+
+	TP_PROTO(enum cfs_idle_inject_action action, int throttled),
+
+	TP_ARGS(action, throttled),
+
+	TP_STRUCT__entry(
+		__field(enum cfs_idle_inject_action, action)
+		__field(int, throttled)
+	),
+
+	TP_fast_assign(
+		__entry->action = action;
+		__entry->throttled = throttled;
+	),
+
+	TP_printk("action:%d throttled:%d", __entry->action, __entry->throttled)
+);
+#endif
+
 #endif /* _TRACE_SCHED_H */
 
 /* This part must be outside protection */
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a0cd777..20027eb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5248,8 +5248,10 @@ idle:
 	if (in_forced_idle(cfs_rq)) {
 		if (unlikely(local_softirq_pending())) {
 			__unthrottle_cfs_rq(cfs_rq);
+			trace_sched_cfs_idle_inject(CFS_IDLE_INJECT_YIELD_SOFTIRQ, 1);
 			goto again;
 		}
+		trace_sched_cfs_idle_inject(CFS_IDLE_INJECT_FORCED, 1);
 		return NULL;
 	}
 	/*
@@ -8432,6 +8434,7 @@ static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *hrtimer)
 		throttle_rq(cpu);
 	}
 	raw_cpu_write(idle_injected, !status);
+	trace_sched_cfs_idle_inject(CFS_IDLE_INJECT_TIMER, !status);
 
 	return HRTIMER_RESTART;
 }
-- 
1.9.1