linux-kernel - Re: [PATCH 1/1] ftrace - add support for tracing_thresh to function

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Message-ID: <20100222181400.GE5055@nowhere>
Date:	Mon, 22 Feb 2010 19:14:02 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Steven Rostedt <srostedt@...hat.com>,
	Tim Bird <tim.bird@...sony.com>,
	linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] ftrace - add support for tracing_thresh to
	function_graph tracer

On Mon, Feb 22, 2010 at 09:48:03AM -0500, Steven Rostedt wrote:
> On Sat, 2010-02-20 at 15:21 +0100, Frederic Weisbecker wrote:
> 
> > 
> > Actually why do we encumber with both tracing_thresh and the funcgraph-exit
> > option?
> > 
> > We could just have the output and the record check tracing_thresh instead
> > of the funcgraph-exit option.
> 
> You mean just use tracing_thresh during the tracing? We could perhaps
> also change the code (and I think this would be beneficial even without
> this change) to print the function on exit if it did not have a entry.
> 
> That is, in the reading of the trace, keep a depth pointer. For every
> "entry" we hit, we add one, and for every "exit" we subtract one (per
> cpu). If we go negative, we keep the counter at zero, but write
> something like:
> 
> 
>   } (sys_write)



Why not, looks like a good idea.


> 
> Because I always hate it when a trace starts with a bunch of "}" and I
> have no idea what functions they are. This would fix that.


Agreed.



> Yeah, Tim's trace would have only "} (sys_write)" type syntax but that's
> probably fine.



May be. Or we can couple your above solution and check if tracing_thresh > 0,
in which case we just zap the "}".

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