linux-kernel - Re: [tip:timers/tracing] hrtimer: Add tracepoint for hrtimers

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Message-Id: <1255404309.7113.948.camel@gandalf.stny.rr.com>
Date:	Mon, 12 Oct 2009 23:25:09 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	mingo@...hat.com, hpa@...or.com, mathieu.desnoyers@...ymtl.ca,
	anton@...ba.org, linux-kernel@...r.kernel.org,
	peterz@...radead.org, zhaolei@...fujitsu.com,
	xiaoguangrong@...fujitsu.com, fweisbec@...il.com,
	tglx@...utronix.de, kosaki.motohiro@...fujitsu.com
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:timers/tracing] hrtimer: Add tracepoint for hrtimers

On Wed, 2009-09-02 at 12:18 +0000, tip-bot for Xiao Guangrong wrote:

> +/**
> + * hrtimer_start - called when the hrtimer is started
> + * @timer: pointer to struct hrtimer
> + */
> +TRACE_EVENT(hrtimer_start,
> +
> +	TP_PROTO(struct hrtimer *timer),
> +
> +	TP_ARGS(timer),
> +
> +	TP_STRUCT__entry(
> +		__field( void *,	timer		)
> +		__field( void *,	function	)
> +		__field( s64,		expires		)
> +		__field( s64,		softexpires	)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->timer		= timer;
> +		__entry->function	= timer->function;
> +		__entry->expires	= hrtimer_get_expires(timer).tv64;
> +		__entry->softexpires	= hrtimer_get_softexpires(timer).tv64;
> +	),
> +
> +	TP_printk("hrtimer %p, func %pf, expires %llu, softexpires %llu",
> +		  __entry->timer, __entry->function,
> +		  (unsigned long long)ktime_to_ns((ktime_t) {
> +				  .tv64 = __entry->expires }),
> +		  (unsigned long long)ktime_to_ns((ktime_t) {
> +				  .tv64 = __entry->softexpires }))
> +);
> +

I was just fixing up the trace-cmd parser (which is also used for perf)
and came across this code. That TP_printk shows up in the format file
as:

print fmt: "hrtimer %p, func %pf, expires %llu, softexpires %llu", REC->timer, REC->function, (unsigned long long)(((ktime_t) { .tv64 = REC->expires }).tv64), (unsigned long long)(((ktime_t) { .tv64 = REC->softexpires }).tv64)

Now I'm trying to parse this with a tool so that we can have something
that can read the binary output, and be able to easily figure it out by
reading the format files. But trying to parse:

(unsigned long long)(((ktime_t) { .tv64 = REC->expires }).tv64)

Is not easy. It's basically implementing a C interpreter :-(

Is there anyway we can change that TRACE_EVENT to give us a better,
trace printk output?

-- Steve


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