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 <leo....@linaro.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 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 <leo....@linaro.org> Reviewed-by: Mathieu Poirier <mathieu.poir...@linaro.org> Cc: Alexander Shishkin <alexander.shish...@linux.intel.com> Cc: Jiri Olsa <jo...@redhat.com> Cc: Mike Leach <mike.le...@linaro.org> Cc: Namhyung Kim <namhy...@kernel.org> Cc: Robert Walker <robert.wal...@arm.com> Cc: coresight ml <coresi...@lists.linaro.org> Cc: linux-arm-ker...@lists.infradead.org Link: http://lkml.kernel.org/r/1544513908-16805-7-git-send-email-leo....@linaro.org Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.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);