linux-kernel - Re: [PATCH] Add function graph tracer support for ARM

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Message-ID: <20090423221516.GB5976@nowhere>
Date:	Fri, 24 Apr 2009 00:15:17 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Tim Bird <tim.bird@...sony.com>
Cc:	Uwe � <u.kleine-koenig@...gutronix.de>,
	linux kernel <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>,
	linux-arm-kernel <linux-arm-kernel@...ts.arm.linux.org.uk>,
	Russell King <rmk@....linux.org.uk>
Subject: Re: [PATCH] Add function graph tracer support for ARM

On Thu, Apr 23, 2009 at 02:49:56PM -0700, Tim Bird wrote:
> Uwe � wrote:
> >> Signed-off-by: <tim.bird@...sony.com>
> > According to Documentation/SubmittingPatches you need to provide your
> > real name in the S-o-b line.
> 
> OK -that's embarrassing - I'll fix this.
> scripts/checkpatch.pl didn't catch this.  I may look at adding
> something to checkpatch.pl to catch empty names.
> 
> > For the lazy of us, can you point me^Uus to some documentation how to
> > use the graph tracer?
> 
> It looks like Documentation/ftrace.txt is missing anything about
> function graph tracing.
> 
> Should I add a section?



There is already a section in Documentation/frace.txt as well in 2.6.30 :-)



> 
> Here are some quick steps:
> 
> $ mount -t debugfs none /debug
> $ cd /debug/tracing/
> $ cat available_tracers
> function_graph function sched_switch nop
> $ echo function_graph >current_tracer
> $ cat trace
> # tracer: function_graph
> #
> # CPU OVERHEAD/DURATION            FUNCTION CALLS
> # |   |        |                   |   |   |   |
>  ------------------------------------------
>  0)      --1       =>   events/-5
>  ------------------------------------------
> 
>  0)               |                activate_task() {
>  0)               |                  enqueue_task() {
>  0)               |                    enqueue_task_fair() {
>  0)               |                      update_curr() {
>  0)   0.000 us    |                        calc_delta_mine();
>  0)   0.000 us    |                        update_min_vruntime();
>  0) + 61.035 us   |                      }
>  0)   0.000 us    |                      place_entity();
>  0)   0.000 us    |                      __enqueue_entity();
>  0) + 91.552 us   |                    }
>  0) ! 122.070 us  |                  }
>  0) ! 152.588 us  |                }
>  0)               |                check_preempt_wakeup() {
>  0)   0.000 us    |                  update_curr();
>  0)   0.000 us    |                  wakeup_preempt_entity();
>  0) + 61.035 us   |                }
> 
> Clearly, my clock stinks, but that's a separate issue.


Oh, that's the first function graph trace from Arm I can see.
/me feels a bit moved...

Just one childish caprice...it would be nice to see a part of a
trace which shows specific Arm arch functions in the next changelog :-)


Thanks,
Frederic.

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