linux-kernel - Re: [PATCH v3 0/8] perf cs-etm: Correct packets handling

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Date:   Wed, 12 Dec 2018 11:45:44 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Leo Yan <leo.yan@...aro.org>,
        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 Mailing List <linux-kernel@...r.kernel.org>,
        Coresight ML <coresight@...ts.linaro.org>
Subject: Re: [PATCH v3 0/8] perf cs-etm: Correct packets handling

On Tue, 11 Dec 2018 at 00:40, Leo Yan <leo.yan@...aro.org> wrote:
>
> perf cs-etm module converts decoder elements to packets and then we have
> more context crossing packets to generate synthenize samples, finally
> perf tool can faciliate samples for statistics and report the results.
>
> This patch series is to address several issues found related with
> packets handling and samples generation when worked firstly on branch
> sample flags support for Arm CoreSight trace data, so this patch series
> is dependency for sample flags setting, will send another dedicated
> patch series for sample flags later.
>
> In this patch series, the first two patches are mainly to fix issues in
> cs_etm__flush(): patch 0001 corrects packets swapping in cs_etm__flush()
> and this can fix the wrong branch sample caused by the missed packets
> swapping; patch 0002 is to fix the wrong samples generation with stale
> packets at the end of trace block.
>
> Patch 0003 and 0004 are for minor fixing; patch 0003 removes unused field
> 'cs_etm_decoder::trace_on', this can simplize the switch-case code for all
> discontinuity packet generation by using one code block; patch 0004 is to
> refactor enumeration cs_etm_sample_type.
>
> Patch 0005 is to rename CS_ETM_TRACE_ON to CS_ETM_DISCONTINUITY, we use
> a more general packet type to present trace discontinuity, so it can be
> used by TRACE_ON event, and also can be used by NO_SYNC and EO_TRACE
> elements.
>
> Patch 0006 is used to support NO_SYNC packet, otherwise the trace
> decoding cannot reflect the tracing discontinuity caused by NO_SYNC
> packet.
>
> Patch 0007 is used to support EO_TRACE packet, which also introduces
> the tracing discontinuity at the end of trace and we should save last
> trace data for it.
>
> Patch 0008 is used to generate branch sample for exception packets.
>
> Credit to Mike Leach and Robert Walker who made me clear for underlying
> mechanism for NO_SYNC/EO_TRACE elements, Mike also shared the detailed
> explanation for why we can treat NO_SYNC and TRACE_ON elements as the
> same, so except following Mike & Rob suggestion for trace discontinuity
> consolidation, most commit log of patches 0006/0007 also come from
> Mike's explanation.
>
> This patch series is applied directly on the acme's perf/core branch [1]
> with latest commit aaab25f03e9e ("perf trace: Allow selecting use the
> use of the ordered_events code").
>
> With applying the dependency patch, this patch series has been tested
> for branch samples dumping with below command on Juno board:
>
>   # perf script -F,-time,+ip,+sym,+dso,+addr,+symoff -k vmlinux

Good day Arnaldo,

I have reviewed all the changes in this set - please consider adding
to your next branch.  Let me know if you want a pull request.

Regards,
Mathieu

>
> Changes from v2:
> * Addressed Mathieu's comments and suggestions for minor refactoring
>   for removing unused field 'cs_etm_decoder::trace_on' and added one
>   dedicated patch to refactor enumeration cs_etm_sample_type.
> * Added Mathieu's 'reviewed' tags;  Very appreciate Mathieu's many
>   suggestion for crossing several patch series.
>
> Changes from v1:
> * Synced the consistent code in patch 0001 for condition checking.
> * Introduced new function cs_etm__end_block() for flushing packet
>   at the end of trace block.
> * Added new patch 0003 to rename CS_ETM_TRACE_ON to
>   CS_ETM_DISCONTINUITY.
> * Used the same one packet type CS_ETM_DISCONTINUITY for all
>   trace discontinuity (include support TRACE_ON/EO_TRACE/NO_SYNC
>   packets).
> * Removed tracking exception number patch, which will be added in
>   sample flag patch series.
>
>
> Leo Yan (8):
>   perf cs-etm: Correct packets swapping in cs_etm__flush()
>   perf cs-etm: Avoid stale branch samples when flush packet
>   perf cs-etm: Remove unused 'trace_on' in cs_etm_decoder
>   perf cs-etm: Refactor enumeration cs_etm_sample_type
>   perf cs-etm: Rename CS_ETM_TRACE_ON to CS_ETM_DISCONTINUITY
>   perf cs-etm: Treat NO_SYNC element as trace discontinuity
>   perf cs-etm: Treat EO_TRACE element as trace discontinuity
>   perf cs-etm: Generate branch sample for exception packet
>
>  tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 42 +++++++++-----
>  tools/perf/util/cs-etm-decoder/cs-etm-decoder.h | 10 ++--
>  tools/perf/util/cs-etm.c                        | 77 ++++++++++++++++++++++---
>  3 files changed, 100 insertions(+), 29 deletions(-)
>
> --
> 2.7.4
>