Re: [RFC PATCH 5/5] perf: Implement perf_output_addr()

From: Frederic Weisbecker
Date: Wed May 19 2010 - 05:03:21 EST

On Wed, May 19, 2010 at 09:58:02AM +0200, Peter Zijlstra wrote:
> On Wed, 2010-05-19 at 09:21 +0200, Frederic Weisbecker wrote:
> > I'm still not sure what you mean here by this multiplexing. Is
> > this about per cpu multiplexing?
> Suppose there's two events attached to the same tracepoint. Will you
> write the tracepoint twice and risk different data in each, or will you
> do it once and copy it into each buffer?

The only different data we risk in each is the timestamp, which is
something we can probably fetch once before actually filling the

> > There is another problem. We need something like
> > perf_output_discard() in case the filter reject the event (which
> > must be filled for this check to happen).
> Yeah, I utterly hate that, I opted to let anything with a filter take
> the slow path. Not only would I have to add a discard, but I'd have to
> decrement the counter as well, which is a big no-no.

That makes it complicated. But for now we don't have much other solutions.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at