linux-kernel - Re: [PATCH V6 08/17] perf tools: Add Intel PT support

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Date:	Thu, 25 Jun 2015 21:09:58 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Jiri Olsa <jolsa@...hat.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH V6 08/17] perf tools: Add Intel PT support

Em Thu, Jun 25, 2015 at 08:56:34PM -0300, Arnaldo Carvalho de Melo escreveu:
> Will do the same tests with intel_pt as well, on a remote machine, add examples
> to the changeset logs and everything going well, aim for pushing for Ingo soon,

So, I asked for callchains, with:

 perf record -g -e intel_bts// ls

And it got stuck somewhere, then I did a perf top to see where it was,
and got to:

  96.24%  perf    [.] intel_bts_process_queue

Annotating I get to:

  1.17 │1a0:┌─→mov    0x8(%r13),%rdx
       │    │  test   %rdx,%rdx
 98.83 │    └──je     1a0


Which is an endless loop! Source code for intel_bts_process_buffer(),
inlined there:

        while (sz > sizeof(struct branch)) {
                if (!branch->from && !branch->to)
                        continue;
                err = intel_bts_synth_branch_sample(btsq, branch);
                if (err)
                        break;
                branch += 1;
                sz -= sizeof(struct branch);
        }

Can you fix this, please, so that I can fold it into where it was
introduced, namely:

commit 439ad895a2aecea09416206f023336297cc72efe
Author: Adrian Hunter <adrian.hunter@...el.com>
Date:   Fri May 29 16:33:39 2015 +0300

    perf tools: Add Intel BTS support

- Arnaldo
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