lkml.org 
[lkml]   [2008]   [Sep]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC PATCH 1/3] Unified trace buffer

    * Steven Rostedt <rostedt@goodmis.org> 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! :)

    Ingo


    \
     
     \ /
      Last update: 2008-09-27 20:51    [W:0.022 / U:32.256 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site