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Subject: Re: [PATCH][RFC] tracing: Enable tracepoints via module parameters
From: Steven Rostedt <rostedt@goodmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Yuanhan Liu <yuanhan.liu@linux.intel.com>,
        chris <chris@chris-wilson.co.uk>
In-Reply-To: <20110308232258.GA25987@Krystal>
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	 <20110308232258.GA25987@Krystal>
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Date: Tue, 08 Mar 2011 18:32:55 -0500
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On Tue, 2011-03-08 at 18:22 -0500, Mathieu Desnoyers wrote:
> * Steven Rostedt (rostedt@goodmis.org) wrote:
> > A few months ago it was suggested to have a way to enable tracepoints in
> > a module when it is loaded. I tried various methods, but this one seems
> > to be the least intrusive. In fact, it requires no modification to the
> > module code.
> > 
> > The trace event now adds its own MODULE_INFO() and kernel_param_ops that
> > and links the information about a tracepoint into the module's __param
> > section. A module can be loaded with a tracepoint active by adding
> > trace_<tracepoint>=1 as one of the parameters.
> 
> Hi Steven,
> 
> Can you walk me through the expected sequence someone wanting to enable a few
> specific module tracepoints would have to go through ? I'm thinking here about
> the context of a distro which has on-demand module loading. The scenario I am
> thinking about is a distro specifying a basic set of tracepoints to enable in a
> "standard catch-all tracing configuration", which includes some tracepoints in
> yet-unloaded modules. I'm trying to figure out what the end user experience will
> look like if we go for the solution you propose here.
> 

You would add it like any other module parameter.

Just update it in your /etc/modprobe.d/ directory.

-- Steve


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