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
adiscontinuity 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.yan@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.yan@linaro.org Reviewed-by: Mathieu Poirier mathieu.poirier@linaro.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Jiri Olsa jolsa@redhat.com Cc: Mike Leach mike.leach@linaro.org Cc: Namhyung Kim namhyung@kernel.org Cc: Robert Walker robert.walker@arm.com Cc: coresight ml coresight@lists.linaro.org Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1544513908-16805-7-git-send-email-leo.yan@linaro.or... Signed-off-by: Arnaldo Carvalho de Melo acme@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);