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Received: from [190.15.121.82] (helo=quaco.ghostprotocols.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gXQJR-0003uA-4P for linux-arm-kernel@lists.infradead.org; Thu, 13 Dec 2018 12:41:57 +0000 Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id BC88341B1D; Thu, 13 Dec 2018 09:41:54 -0300 (-03) Date: Thu, 13 Dec 2018 09:41:54 -0300 From: Arnaldo Carvalho de Melo To: Leo Yan Subject: Re: [PATCH v3 6/8] perf cs-etm: Treat NO_SYNC element as trace discontinuity Message-ID: <20181213124154.GF21027@kernel.org> References: <1544513908-16805-1-git-send-email-leo.yan@linaro.org> <1544513908-16805-7-git-send-email-leo.yan@linaro.org> <20181213123854.GE21027@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20181213123854.GE21027@kernel.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mathieu Poirier , Alexander Shishkin , Coresight ML , linux-kernel@vger.kernel.org, Namhyung Kim , Robert Walker , Jiri Olsa , linux-arm-kernel@lists.infradead.org, Mike Leach Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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: commit 148068b45fe2e93b19c06cfc1140ea12ca72eb59 Author: Leo Yan 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 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 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, 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 Reviewed-by: Mathieu Poirier Cc: Alexander Shishkin Cc: Jiri Olsa Cc: Mike Leach Cc: Namhyung Kim Cc: Robert Walker Cc: coresight ml Cc: linux-arm-kernel@lists.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 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); _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel