linux-kernel - Re: [PATCH v3 1/5] perf cs-etm: Swap packets for instruction samples

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Date:   Thu, 6 Feb 2020 15:43:28 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Mike Leach <mike.leach@...aro.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel@...r.kernel.org,
        Robert Walker <robert.walker@....com>,
        Coresight ML <coresight@...ts.linaro.org>
Subject: Re: [PATCH v3 1/5] perf cs-etm: Swap packets for instruction samples

Hi Mike,

On Wed, Feb 05, 2020 at 03:59:40PM +0000, Mike Leach wrote:
> Hi Leo
> 
> On Mon, 3 Feb 2020 at 01:52, Leo Yan <leo.yan@...aro.org> wrote:
> >
> > If use option '--itrace=iNNN' with Arm CoreSight trace data, perf tool
> > fails inject instruction samples; the root cause is the packets are
> > only switched for branch samples and last branches but not for
> > instruction samples, so the new coming packets cannot be properly
> > handled for only synthesizing instruction samples.
> >
> > To fix this issue, this patch switches packets for instruction samples.
> >
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> > ---
> >  tools/perf/util/cs-etm.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> > index 5471045ebf5c..3dd5ba34a2c2 100644
> > --- a/tools/perf/util/cs-etm.c
> > +++ b/tools/perf/util/cs-etm.c
> > @@ -1404,7 +1404,8 @@ static int cs_etm__sample(struct cs_etm_queue *etmq,
> >                 }
> >         }
> >
> > -       if (etm->sample_branches || etm->synth_opts.last_branch) {
> > +       if (etm->sample_branches || etm->synth_opts.last_branch ||
> > +           etm->sample_instructions) {
> >                 /*
> >                  * Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for
> >                  * the next incoming packet.
> > @@ -1476,7 +1477,8 @@ static int cs_etm__flush(struct cs_etm_queue *etmq,
> >         }
> >
> >  swap_packet:
> > -       if (etm->sample_branches || etm->synth_opts.last_branch) {
> > +       if (etm->sample_branches || etm->synth_opts.last_branch ||
> > +           etm->sample_instructions) {
> >                 /*
> >                  * Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for
> >                  * the next incoming packet.
> > --
> > 2.17.1
> >
> if is worth putting the 'if <options> { swap packet }' into a separate
> function as it appears twice in identical form? Might help if more
> options for swap packet are needed later.

Makes sense.  Will factor out a new function for this.

Thanks for reviewing!
Leo

> Either way
> 
> Reviewed by: Mike Leach <mike.leach@...aro.org>
> 
> 
> -- 
> Mike Leach
> Principal Engineer, ARM Ltd.
> Manchester Design Centre. UK