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    SubjectRe: [PATCH][RFC] tracing: Enable tracepoints via module parameters
    * Steven Rostedt (rostedt@goodmis.org) wrote:
    > 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.

    So what you are saying here is that modifying /etc/modprobe.d/ is the actual
    interface you propose presenting to the end-users to control their tracepoints ?

    Maybe I am missing something, but this interface seems to lack the layer of
    finish we might want to put into a user-visible API. I don't really see how
    distributions can hope to automate any of this for their end-user without making
    a mess of the /etc/modprobe.d/ they ship with.

    Thanks,

    Mathieu

    --
    Mathieu Desnoyers
    Operating System Efficiency R&D Consultant
    EfficiOS Inc.
    http://www.efficios.com


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