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

[KOSAKI Motohiro]

> 
> 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+0x0/0xf0
> <idle>-0     [000]   264.040508: hrtimer_exit: func=.tick_sched_timer+0x0/0xf0 restart=HRTIMER_RESTART
> <idle>-0     [000]   264.040530: timer_entry: func=.e1000_watchdog+0x0/0x8fc
> <idle>-0     [000]   264.040728: timer_exit: func=.e1000_watchdog+0x0/0x8fc
> 
> 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@xxxxxxxxx>

This patch don't cover all timer life-cycle. but I think it's good start.
At least, you prove this patch can find one issue :)

 - kosaki

> ---
> 
> Index: linux-2.6-tracing/kernel/hrtimer.c
> ===================================================================
> --- linux-2.6-tracing.orig/kernel/hrtimer.c	2009-05-20 17:11:50.000000000 +1000
> +++ linux-2.6-tracing/kernel/hrtimer.c	2009-05-20 17:11:52.000000000 +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-tracing/kernel/timer.c
> ===================================================================
> --- linux-2.6-tracing.orig/kernel/timer.c	2009-05-20 17:11:50.000000000 +1000
> +++ linux-2.6-tracing/kernel/timer.c	2009-05-20 17:11:52.000000000 +1000
> @@ -44,6 +44,9 @@
>  #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);
> @@ -946,7 +949,9 @@
>  				 */
>  				lock_map_acquire(&lockdep_map);
>  
> +				trace_timer_entry(timer);
>  				fn(data);
> +				trace_timer_exit(timer);
>  
>  				lock_map_release(&lockdep_map);
>  
> Index: linux-2.6-tracing/include/trace/events/timer.h
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6-tracing/include/trace/events/timer.h	2009-05-20 17:15:41.000000000 +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>
> --
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