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    SubjectRe: LTTng kernel integration roadmap, update

    On Mon, 24 Nov 2008, Mathieu Desnoyers wrote:
    > The key idea behind this is to answer to Thomas Gleixner concerns, who
    > supports that a tracer should output data in text-format only so it can
    > be used with tools kernel developers have on their system, like "cat".
    > However, getting data out of the kernel efficiently simply cannot be
    > done with such approach. Therefore, LTTng needs its own userspace tools
    > to splice the data out of the kernel efficiently. Another tool is used
    > to pretty-print the binary data into text.
    > Then the problem becomes : we have to make the userspace tool easy
    > enough to deploy so even Linus can find and use it. ;)
    > But indeed, the trace buffers are versioned, so if the format changes
    > between kernel versions, the userspace tools will detect it and the user
    > will know it must update its tools. So it's not really a problem there.
    > The question that prevails is therefore : should we ship userspace
    > binary with the kernel tree at all ? And if yes, how should the resuting
    > executables be packaged and deployed ? Should it be installed in the
    > system along with kernel modules or should it be populated into a
    > filesystem populated by kernelspace ?
    > Or is it better to do as we have always done and keep the userspace
    > tools separated from the kernel tree ?

    I say keep the user space tools separate as much as possible.

    What about having a meta-data file for all binary files. This meta-data
    could explain the format that is read. Big endian, little endian, the
    fields and offsets, the event ids etc. This way we will not need a
    "version" file, which means absolutely nothing if you do not know what
    comes with that version. Any tool could look at the meta-data file and
    figure out what is in the buffers.

    -- Steve

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