linux-kernel - Re: [PATCH v2 1/3] ftrace: add tracepoint for timer

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Date:	Tue, 7 Jul 2009 19:39:50 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Zhaolei <zhaolei@...fujitsu.com>, kosaki.motohiro@...fujitsu.com,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] ftrace: add tracepoint for timer

On Tue, Jul 07, 2009 at 05:28:18PM +0800, Xiao Guangrong wrote:
> 
> 
> Thomas Gleixner wrote:
> > On Mon, 6 Jul 2009, Xiao Guangrong wrote:
> >> Changelog v1->v2:
> >> 1: Add jiffies info into timer
> >> 2: Combine debugobjects and trace as Thomas's suggestion
> > 
> > I like it that way. Some minor nitpicks below.
> >  
> >> +TRACE_EVENT(timer_expire,
> >> +
> >> +	TP_PROTO(struct timer_list *timer),
> >> +
> >> +	TP_ARGS(timer),
> >> +
> >> +	TP_STRUCT__entry(
> >> +		__field( void *,	timer		)
> >> +		__field( void *,	function	)
> > 
> >   Do we really need the function here? It does not change between
> >   start and expiry.
> > 
> 
> Yeah, I'll fix.
> 
> >> +TRACE_EVENT(timer_cancel,
> >> +
> >> +	TP_PROTO(struct timer_list *timer),
> >> +
> >> +	TP_ARGS(timer),
> >> +
> >> +	TP_STRUCT__entry(
> >> +		__field( void *,	timer		)
> >> +		__field( void *,	function	)
> > 
> >   Ditto.
> > 
> 
> Will fix.
> 
> >> +
> >> +static inline void debug_and_trace_timer_expire(struct timer_list *timer)
> > 
> >   Technically not really necessary. The debug code does not care about
> >   it.
> > 
> 
> Will fix.
> 
> >>  			timer = list_first_entry(head, struct timer_list,entry);
> >> +			debug_and_trace_timer_expire(timer);
> >>  			fn = timer->function;
> >>  			data = timer->data;
> >>  
> > 
> > Can you please add the tracepoint which was suggested by Anton (IIRC)
> > which allows us to measure the execution time of the callback function
> > ? There is no need to dereference timer in the expiry tracepoint, we
> > just store the pointer. So we can safely move the tracepoints just
> > around the function call.
> > 
> >    trace_timer_expire(timer);
> >    fn(data);
> >    trace_timer_callback_done(timer);
> > 
> > Or whatever fancy name you come up with.
> > 
> 
> OK, I'll fix it base on your suggestion.
>  
> trace_timer_expire/trace_timer_callback_done are already in Frederic' tree
> but with different name, see below URL:
>  	http://marc.info/?l=linux-kernel&m=124331396919301&w=2
>  
> I'll modify those tracepoint's name to match ours.
>  
> Thank you very much!
>  
> Xiao


If you wish so, I can gather your patches with the one of Anton Blanchard
and send a pull request once it's acked.

Thanks,
Frederic.

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