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    SubjectRe: [PATCH -tip tracing/kprobes 0/9] tracing/kprobes, perf: perf probe and kprobe-tracer bugfixes

    * Frederic Weisbecker <fweisbec@gmail.com> wrote:

    [...]
    >
    > I think absolute and relative line modes are not colliding/contending
    > at all but actually fit two different needs.

    Definitely so.

    > - absolute is nice when you are lonely doing kernel debugging.
    > (can be expanded at will once you imagine user probes)
    > You are stuck in your code editor, trying to figure out the
    > origin of your problem and then you think it would be nice
    > to set a probe in branch 1 and in branch 2 inside func_foo().
    > Then you already have absolute lines and relying in
    > perf probe --list func_foo() to resolve an absolute line into
    > a relative one is a very undesired middle step.

    Of course - absolute numbers definitely rule for everything that works
    on a whole-file basis. (I'd argue that if you do that from an editor
    then you want a short macro that just sets a probe there - much like a
    breakpoint. Such an editor macro would want to use absolute numbers.))

    > - relative is nice in some other cases. When you already have
    > the function target in mind, you even don't need to check your
    > editor, just a quick check to this command and get the relative
    > line. But also when you want to transmit a probe reference
    > in a mailing list because of its better lifetime.

    also useful for command line workflows: 'perf probe --list' output - i
    think we users to generate func_symbol+rel_position kind of probes.

    Plus a relative position is more intuitive as well. If you see
    'schedule+10' versus 'schedule+102', you'll know it immediate that the
    first one is early in the function while the second one is near the end.

    If you see 'schedule@2465' versus 'schedule@2555' that kind of 'where in
    the function is the probe, roughly' subjective impression is lost.

    Ingo


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