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    SubjectRe: [RFC PATCH 1/3] Unified trace buffer

    * Steven Rostedt <> wrote:

    > On Sat, 27 Sep 2008, Ingo Molnar wrote:
    > >
    > > If all you do is to trace high-freq events on all CPUs and you are _not_
    > > interested in the precise interactions, the overhead of global
    > > synchronization can hurt a lot.
    > >
    > > In any case, SMP coherency of trace events is an independent property of
    > > the tracer, and preferably something that can be turned on/off.
    > Just a note. The current ring buffering system that I'm proposing
    > keeps its own time stamp counter (currently sched_clock) that will
    > most likely be updated later. I'm trying to keep this ring buffer
    > system as dumb as possible. It does not even implement the merge sort.
    > That's up to the tracer to handle. There's nothing stopping the trace
    > from adding some atomic counter to each event to help it sort.

    correct. The price is all the notifier/callback overhead and the loss of
    type checking of the record contents. But that's an unavoidable price of
    abstraction, at least in C.

    > So yes, the tracer can implement anything it wants on top of the ring
    > buffer ;-)

    yes, very nice! :)


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