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

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Date:	Fri, 13 Nov 2015 11:53:07 -0800
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <len.brown@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Paul Turner <pjt@...gle.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH 4/4] sched: add trace event for idle injection

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@...ux.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

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