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    SubjectRe: [PATCH 0/5][RFC] [RFC] function profiler

    * Steven Rostedt <rostedt@goodmis.org> wrote:

    > The following patches are RFC, and to discuss is this work would
    > be useful.
    >
    > This patch series adds a function profiler hook to the function
    > tracer and function graph tracer. That is, it uses the mcount
    > calls to track the functions being called. Now with the function
    > graph tracer it also keeps track of the times the functions have
    > been executing.
    >
    > Note, this is similar to oprofile, but is not a sampling approach,
    > but a true recorder. Of course, by recording every function the
    > overhead compared to oprofile is higher. With the use of dynamic
    > ftrace, you could just trace certain functions, or just a certain
    > module. The flexibility is a bit greater with this profiling.

    Also, with the built-in user-defined filter code in the latest
    tracing tree this can also be used to only trace a given PID, or a
    range of PIDs.

    Or we can trace preempt-disabled functions only, via this filter
    expression:

    echo 'common_preempt_count != 0' > /debug/tracing/events/ftrace/function/filter

    Or (future planned) we can profile functions only taking longer than
    100 microseconds:

    echo 'duration >= 0' > /debug/tracing/events/ftrace/function/filter

    There are other possibilities as well.

    Ingo


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