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Message-ID: <20181213132126.GI21027@kernel.org>
Date: Thu, 13 Dec 2018 10:21:26 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: leo.yan@...aro.org
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Coresight ML <coresight@...ts.linaro.org>,
Mike Leach <mike.leach@...aro.org>,
Robert Walker <robert.walker@....com>
Subject: Re: [PATCH v3 6/8] perf cs-etm: Treat NO_SYNC element as trace
discontinuity
Em Thu, Dec 13, 2018 at 09:09:49PM +0800, leo.yan@...aro.org escreveu:
> Hi Arnaldo,
>
> On Thu, Dec 13, 2018 at 09:41:54AM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Dec 13, 2018 at 09:38:54AM -0300, Arnaldo Carvalho de Melo escreveu:
> > > Em Tue, Dec 11, 2018 at 03:38:26PM +0800, Leo Yan escreveu:
> > > > CoreSight tracer driver might insert barrier packet between different
> > > > buffers, thus the decoder can spot the boundaries based on the barrier
> > > > packet; the decoder is possible to hit a barrier packet and emit a
> > > > NO_SYNC element, then the decoder will find a periodic synchronisation
> > > > point inside that next trace block that starts trace again but does not
> > > > have the TRACE_ON element as indicator - usually because this block of
> > > > trace has wrapped the buffer so we have lost the original point that
> > > > trace was enabled.
> > > >
> > > > In upper case, it results in the trace stream only inserts the
> > > > OCSD_GEN_TRC_ELEM_NO_SYNC element in the middle of tracing stream, but
> > > > we don't handle NO_SYNC element properly and at the end users miss to
> > > > see the info for trace discontinuity.
> > >
> > >
> > > "In upper case"? Maybe:
> > >
> > > In the former case it causes the insertion of a OCSD_GEN_TRC_ELEM_NO_SYNC
> > > in the middle of the the tracing stream, but as we were npt handling the
> > > NO_SYNC element properly which ends up making users miss the
> > > discontinuity indication"?
> >
> > > > Though OCSD_GEN_TRC_ELEM_NO_SYNC is different from CS_ETM_TRACE_ON when
> > > > output from the decoder, but both of them indicate the trace data is
> > >
> > > can we remove the "but" and "of them" (redundant) above?
> > >
> > > > discontinuous; this patch treats OCSD_GEN_TRC_ELEM_NO_SYNC as trace
> > > a
> > > > discontinuity and generates CS_ETM_DISCONTINUITY packet for it, so
> > > > cs-etm can handle discontinuity for this case, finally it saves the last
> > > it (way too many "discontinuity")
> > > > trace data for previous trace block and restart samples for new block.
> >
> > I've tentatively done those changes (and a few more) in my local branch,
> > resulting in the wording below, plese let me know if you are ok with it:
>
> Very appreciate your helping. Please see some minor typos in below
> commit:
>
> > commit 148068b45fe2e93b19c06cfc1140ea12ca72eb59
> > Author: Leo Yan <leo.yan@...aro.org>
> > Date: Tue Dec 11 15:38:26 2018 +0800
> >
> > perf cs-etm: Treat NO_SYNC element as trace discontinuity
> >
> > The CoreSight tracer driver might insert a barrier packets between
> packet
I'll remove the 'a' instead, ok?
> > different buffers, thus the decoder can spot the boundaries based on the
> > barrier packet; it is possible for the decoder to hit a barrier packet
> > and emit a NO_SYNC element, then the decoder will find a periodic
> > synchronisation point inside that next trace block that starts the trace
> > again but does not have the TRACE_ON element as indicator - usually
> > because this trace block has wrapped the buffer so we have lost the
> > original point when the trace was enabled.
> >
> > In the first case it causes the insertion of a OCSD_GEN_TRC_ELEM_NO_SYNC
> former
> > in the middle of the the tracing stream, but as we were npt handling the
> not
> > NO_SYNC element properly which ends up making users miss the
> > discontinuity indication"?
> s/?/.
>
> Thanks a lot for helping. If you prefer me to resend the patch set,
> also let me know.
I can fix it, here.
> > Though OCSD_GEN_TRC_ELEM_NO_SYNC is different from CS_ETM_TRACE_ON when
> > output from the decoder, both indicate that the trace data is
> > discontinuous; this patch treats OCSD_GEN_TRC_ELEM_NO_SYNC as a trace
> > discontinuity and generates a CS_ETM_DISCONTINUITY packet for it, so
> > cs-etm can handle the discontinuity for this case, finally it saves the
> > last trace data for the previous trace block and restart samples for the
> > new block.
> >
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> > Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> > Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> > Cc: Jiri Olsa <jolsa@...hat.com>
> > Cc: Mike Leach <mike.leach@...aro.org>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Robert Walker <robert.walker@....com>
> > Cc: coresight ml <coresight@...ts.linaro.org>
> > Cc: linux-arm-kernel@...ts.infradead.org
> > Link: http://lkml.kernel.org/r/1544513908-16805-7-git-send-email-leo.yan@linaro.org
> > Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> >
> > diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> > index 1039f364f4cc..bee026e76a4c 100644
> > --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> > +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> > @@ -410,7 +410,6 @@ static ocsd_datapath_resp_t cs_etm_decoder__gen_trace_elem_printer(
> > case OCSD_GEN_TRC_ELEM_UNKNOWN:
> > break;
> > case OCSD_GEN_TRC_ELEM_NO_SYNC:
> > - break;
> > case OCSD_GEN_TRC_ELEM_TRACE_ON:
> > resp = cs_etm_decoder__buffer_discontinuity(decoder,
> > trace_chan_id);
> >
> >
--
- Arnaldo
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