linux-kernel - Re: [PATCHv3 0/2] tracing: function graph output for preempt/irqs-off tracers

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Message-ID: <20100329152154.GF1715@jolsa>
Date:	Mon, 29 Mar 2010 17:21:54 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCHv3 0/2] tracing: function graph output for
 preempt/irqs-off tracers

On Mon, Mar 29, 2010 at 11:09:07AM -0400, Steven Rostedt wrote:
> On Mon, 2010-03-29 at 13:17 +0200, Jiri Olsa wrote:
> 
> > >  # echo 0 > /debug/tracing/tracing_enabled
> > >  # echo 0 > /debug/tracing/option/display-graph
> > >  # cat /debug/tracing/trace
> > > 
> > > # tracer: irqsoff
> > > irqbalan-2672    0d..2.   55us+: Unknown type 13
> > > irqbalan-2672    0d.h2.   62us+: Unknown type 13
> > 
> > I forgot the max_tr buffer is actually the one displayed,
> > so it needs reset as well when the display-graph option
> > is switched on/off.
> 
> No! That breaks the rules. It should still show the contents of the
> buffer even if we disable the trace or option.
> 
> 
> > > I think you can still do the "event" part, without effecting the way the
> > > function graph outputs normally. I would not have given up on that
> > > method.  You don't need to worry about it processing other events,
> > > because when you register it to write as an event, it will only be
> > > called when a function graph event was found. It will not be processing
> > > other events. Only when the tracer itself overrides the default writing
> > > will it do so.
> > 
> > The events would be called only for TRACE_GRAPH_RET, TRACE_GRAPH_ENT entries and
> > not for others, thats right.
> > 
> > However it's the graph ouput code that outputs other events' text
> > within "/*" and "*/".
> > 
> > So using the event way, all other events would be printed as normal
> > events(standard lines not alligned) with the standard header...
> > not like comments, as they are in the function_graph tracer.
> > 
> > I thought it'd be good for graph output to stay the same in irqsoff
> > tracer as in function_graph tracer.. if that is not the concern
> > the event way would be probably nicer :)
> 
> It is, but you missed my point.
> 
> > 
> > I'm sending updated patchset with above 2 fixies right away,
> > I can do/resend the event way later if needed.
> 
> What I'm saying is that we should have _both_!  The event way (when the
> option is disabled) and the current way when it is not. That is, if the
> option is enabled, then the function graph can report all the data the
> way it was. If the option is disabled, don't reset it, but have an
> "event" print of the trace as well.
> 
> Understand what I'm trying to ask?

ok, so what you mean is:
- dont clear the max_tr and 
- add function graph events.

So when the tracing_enabled and display-graph are disabled we will
get events output rather than 'unknown event' output... right?

jirka


> 
> -- Steve
> 
> 
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