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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


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