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    SubjectRe: [ANNOUNCE] New utility: 'trace'
    On 11/17/2010 05:02 AM, Peter Zijlstra wrote:
    > On Wed, 2010-11-17 at 13:53 +0100, Frederic Weisbecker wrote:
    >> On Wed, Nov 17, 2010 at 12:35:50PM +0100, Peter Zijlstra wrote:
    >>> On Wed, 2010-11-17 at 09:30 +0100, Ingo Molnar wrote:
    >>>>> For example I'm currently working with dozens of trace_printk() and I would be
    >>>>> very happy to turn some of them off half of the time.
    >>>> I guess we could try such a patch. If you send a prototype i'd be interested in
    >>>> testing it out.
    >>> I don't see the point, the kernel shouldn't contain any trace_printk()s
    >>> to begin with..
    >> It's oriented toward developers. Those who use dozens of tracepoints in
    >> their tree because they are debugging something or developing a new feature,
    >> they might to deactivate/reactivate some of these independant points.
    >> This can also apply to dynamic_printk of course.
    >> Well, the very first and main point is to standardize trace_printk into
    >> a trace event so that it gets usable by perf tools. I have been asked many
    >> times "how to use trace_printk() with perf?".
    > Thing is, since its these dev who add the trace_printk()s to begin with,
    > I don't see the point in splitting them out, if you didn't want them why
    > did you add them to begin with?!

    What I understood from Frederic's email was that during a debug session
    it is sometimes helpful to be able to enable and disable the
    trace_printk's. This makes sense as it reduces the number of kernel
    build/reboot cycles. However, I would think most of that could be
    accomplished with some judicious message tagging and post-processing to
    filter out the unwanted trace_printk's. The only exception might be when
    the trace_printk's add enough overhead to mask a timing related bug. In
    this case, I'd probably be tempted to remove the stubs anyway.

    Darren Hart
    Yocto Linux Kernel

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      Last update: 2010-11-17 19:29    [W:0.027 / U:1.640 seconds]
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