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

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Date:   Wed, 5 Feb 2020 15:59:40 +0000
From:   Mike Leach <mike.leach@...aro.org>
To:     Leo Yan <leo.yan@...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 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.

Either way

Reviewed by: Mike Leach <mike.leach@...aro.org>


-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK