Subject: Re: [RFC] BTS based perf user callchains
From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, Arnaldo Carvalho de Melo <acme@redhat.com>,
        Paul Mackerras <paulus@samba.org>,
        Stephane Eranian <eranian@google.com>,
        Markus Metzger <markus.t.metzger@intel.com>,
        Robert Richter <robert.richter@amd.com>,
        LKML <linux-kernel@vger.kernel.org>
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Date: Mon, 02 Aug 2010 21:47:08 +0200
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On Mon, 2010-08-02 at 20:41 +0200, Frederic Weisbecker wrote:
> On Mon, Aug 02, 2010 at 08:38:52PM +0200, Peter Zijlstra wrote:
> > On Mon, 2010-08-02 at 20:35 +0200, Frederic Weisbecker wrote:
> > > I'm not even sure that will work. Also, while looking at the BTS implementation
> > > in perf, I see we have one BTS buffer per cpu. But that doesn't look right as
> > > the code flow is not linear per cpu but per task. Hence I suspect we need
> > > one BTS buffer per task. But may be someone tried that and encountered a
> > > problem? 
> > 
> > IIRC we flush the buffer when we deschedule the counter.
> 
> 
> Ok. So the buffer is cut on schedule time. It might be nice
> to maintain the buffer progress across scheduling.

We flush it into the perf data buffer.
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