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

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Date:	Tue, 07 Jul 2009 17:28:18 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	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



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

> 
> 	tglx
> 
> 
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