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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 1gXQvf-0004HA-SE for linux-arm-kernel@lists.infradead.org; Thu, 13 Dec 2018 13:21:28 +0000 Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 490D141B1D; Thu, 13 Dec 2018 10:21:26 -0300 (-03) Date: Thu, 13 Dec 2018 10:21:26 -0300 From: Arnaldo Carvalho de Melo To: leo.yan@linaro.org Subject: Re: [PATCH v3 6/8] perf cs-etm: Treat NO_SYNC element as trace discontinuity Message-ID: <20181213132126.GI21027@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> <20181213124154.GF21027@kernel.org> <20181213130949.GB17663@leoy-ThinkPad-X240s> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20181213130949.GB17663@leoy-ThinkPad-X240s> 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 09:09:49PM +0800, leo.yan@linaro.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 > > 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 > > 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); > > > > -- - Arnaldo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel