[PATCH] tracing/events: Add timer and high res timer tracepoints

Anton Blanchard
2009-05-26T04:28:19Z

Add tracepoints for timer and high res timer execution. We add entry and
exit tracepoints so we can calculate timer latency.

Example ftrace output:

<idle>-0 [000] 264.040506: hrtimer_entry: func=.tick_sched_timer
<idle>-0 [000] 264.040508: hrtimer_exit: func=.tick_sched_timer restart=HRTIMER_RESTART
<idle>-0 [000] 264.040530: timer_entry: func=.e1000_watchdog
<idle>-0 [000] 264.040728: timer_exit: func=.e1000_watchdog

Here we can see e1000_watchdog is taking 0.2ms - it might make sense to
move this into a workqueue or kernel thread.

Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
---

v2: Changed %pF to %pf to remove always 0 function offset.

Index: linux-2.6-master/kernel/hrtimer.c
===================================================================
--- linux-2.6-master.orig/kernel/hrtimer.c 2009-05-26 12:55:35.000000000 +1000
+++ linux-2.6-master/kernel/hrtimer.c 2009-05-26 13:09:55.000000000 +1000
@@ -46,6 +46,8 @@

#include <asm/uaccess.h>

+#include <trace/events/timer.h>
+
/**
* ktime_get - get the monotonic time in ktime_t format
*
@@ -1161,7 +1163,9 @@
* the timer base.
*/
spin_unlock(&cpu_base->lock);
+ trace_hrtimer_entry(timer);
restart = fn(timer);
+ trace_hrtimer_exit(timer, restart);
spin_lock(&cpu_base->lock);

/*
Index: linux-2.6-master/kernel/timer.c
===================================================================
--- linux-2.6-master.orig/kernel/timer.c 2009-05-26 12:55:35.000000000 +1000
+++ linux-2.6-master/kernel/timer.c 2009-05-26 13:09:55.000000000 +1000
@@ -45,6 +45,9 @@
#include <asm/timex.h>
#include <asm/io.h>

+#define CREATE_TRACE_POINTS
+#include <trace/events/timer.h>
+
u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;

EXPORT_SYMBOL(jiffies_64);
@@ -947,7 +950,9 @@
*/
lock_map_acquire(&lockdep_map);

+ trace_timer_entry(timer);
fn(data);
+ trace_timer_exit(timer);

lock_map_release(&lockdep_map);

Index: linux-2.6-master/include/trace/events/timer.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6-master/include/trace/events/timer.h 2009-05-26 13:57:42.000000000 +1000
@@ -0,0 +1,116 @@
+#if !defined(_TRACE_TIMER_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_TIMER_H
+
+#include <linux/tracepoint.h>
+#include <linux/timer.h>
+#include <linux/hrtimer.h>
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM timer
+
+/**
+ * timer_entry - called immediately before the timer
+ * @timer: pointer to struct timer_list
+ *
+ * When used in combination with the timer_exit tracepoint we can
+ * determine the timer latency.
+ */
+TRACE_EVENT(timer_entry,
+
+ TP_PROTO(struct timer_list *timer),
+
+ TP_ARGS(timer),
+
+ TP_STRUCT__entry(
+ __field(void *, function)
+ ),
+
+ TP_fast_assign(
+ __entry->function = timer->function;
+ ),
+
+ TP_printk("func=%pf", __entry->function)
+);
+
+/**
+ * timer_exit - called immediately after the timer returns
+ * @timer: pointer to struct timer_list
+ *
+ * When used in combination with the timer_entry tracepoint we can
+ * determine the timer latency.
+ */
+TRACE_EVENT(timer_exit,
+
+ TP_PROTO(struct timer_list *timer),
+
+ TP_ARGS(timer),
+
+ TP_STRUCT__entry(
+ __field(void *, function)
+ ),
+
+ TP_fast_assign(
+ __entry->function = timer->function;
+ ),
+
+ TP_printk("func=%pf", __entry->function)
+);
+
+/**
+ * hrtimer_entry - called immediately before the high res timer
+ * @timer: pointer to struct hrtimer
+ *
+ * When used in combination with the hrtimer_exit tracepoint we can
+ * determine the high res timer latency.
+ */
+TRACE_EVENT(hrtimer_entry,
+
+ TP_PROTO(struct hrtimer *timer),
+
+ TP_ARGS(timer),
+
+ TP_STRUCT__entry(
+ __field(void *, function)
+ ),
+
+ TP_fast_assign(
+ __entry->function = timer->function;
+ ),
+
+ TP_printk("func=%pf", __entry->function)
+);
+
+/**
+ * hrtimer_exit - called immediately after the high res timer returns
+ * @timer: pointer to struct hrtimer
+ * @restart: high res timer return value
+ *
+ * High res timer will restart if @restart is set to HRTIMER_RESTART.
+ * When used in combination with the hrtimer_entry tracepoint we can
+ * determine the high res timer latency.
+ */
+TRACE_EVENT(hrtimer_exit,
+
+ TP_PROTO(struct hrtimer *timer, int restart),
+
+ TP_ARGS(timer, restart),
+
+ TP_STRUCT__entry(
+ __field(void *, function) + __field(int, restart)
+ ),
+
+ TP_fast_assign(
+ __entry->function = timer->function;
+ __entry->restart = restart;
+ ),
+
+ TP_printk("func=%pf restart=%s", __entry->function,
+ (__entry->restart == HRTIMER_RESTART) ?
+ "HRTIMER_RESTART" : "HRTIMER_NORESTART")
+);
+
+#endif /* _TRACE_TIMER_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>