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Date: Fri, 16 Jun 2017 09:06:30 -0700
From: Andi Kleen <ak@linux.intel.com>
To: Stephane Eranian <eranian@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>, "mingo@elte.hu" <mingo@elte.hu>,
        "Liang, Kan" <kan.liang@intel.com>, Jiri Olsa <jolsa@redhat.com>
Subject: Re: [PATCH 0/5] perf: add support for capturing skid IP
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On Thu, Jun 15, 2017 at 11:52:07PM -0700, Stephane Eranian wrote:
> Andi,
> 
> On Thu, Jun 15, 2017 at 4:18 PM, Andi Kleen <ak@linux.intel.com> wrote:
> >> Looking at this approach, the user interface is straightforward,
> >> implementation in the x86 code is a bit more hairy because of the way
> >> the branch_stack is captured, via the cpuc->lbr_entries. If you assume
> >> that SKID_IP cannot be used with any other branch stack mode, then it
> >> is easy. It becomes messy if you don't.
> >
> > That should be fine. After all if you have real LBRs you don't need
> > the skid IP.
> >
> Yes, you still do. This is not the same thing. LBR captures only taken branches.
> I care about taken AND non-taken branches and I don't want to sample on a
> non-taken event, assuming it is available.

Ok that's a reasonable argument for reporting it separately, like
in your original patch.

-Andi