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

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Date:	Tue, 13 Oct 2009 09:08:53 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	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,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:timers/tracing] hrtimer: Add tracepoint for hrtimers


* Steven Rostedt <rostedt@...dmis.org> wrote:

> 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 :-(

Btw., what i suggested quite some time ago was that we should bind 
tracepoints by emitting C source code stubs, which tools can then build 
and link in, using gcc.

	Ingo
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