linux-kernel - [RFT v2 1/4] perf cs-etm: Generate sample for missed packets

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Date:   Mon, 21 May 2018 16:52:25 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tor Jeremiassen <tor@...com>,
        mike.leach@...aro.org, kim.phillips@....com,
        Robert Walker <Robert.Walker@....com>,
        coresight@...ts.linaro.org
Cc:     Leo Yan <leo.yan@...aro.org>, Mike Leach <mike.leach@....com>,
        Robert Walker <robert.walker@....com>
Subject: [RFT v2 1/4] perf cs-etm: Generate sample for missed packets

Commit e573e978fb12 ("perf cs-etm: Inject capabilitity for CoreSight
traces") reworks the samples generation flow from CoreSight trace to
match the correct format so Perf report tool can display the samples
properly.  But the change has side effect for packet handling, it only
generate samples when 'prev_packet->last_instr_taken_branch' is true,
this results in the start tracing packet and exception packets are
dropped.

This patch checks extra two conditions for complete samples:

- If 'prev_packet->sample_type' is zero we can use this condition to
  get to know this is the start tracing packet; for this case, the start
  packet's end_addr is zero as well so we need to handle it in the
  function cs_etm__last_executed_instr();

- If 'prev_packet->exc' is true, we can know the previous packet is
  exception handling packet so need to generate sample for exception
  flow.

Fixes: e573e978fb12 ("perf cs-etm: Inject capabilitity for CoreSight traces")
Cc: Mike Leach <mike.leach@....com>
Cc: Robert Walker <robert.walker@....com>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 tools/perf/util/cs-etm.c | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 822ba91..378953b 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -495,6 +495,13 @@ static inline void cs_etm__reset_last_branch_rb(struct cs_etm_queue *etmq)
 static inline u64 cs_etm__last_executed_instr(struct cs_etm_packet *packet)
 {
 	/*
+	 * The packet is the start tracing packet if the end_addr is zero,
+	 * returns 0 for this case.
+	 */
+	if (!packet->end_addr)
+		return 0;
+
+	/*
 	 * The packet records the execution range with an exclusive end address
 	 *
 	 * A64 instructions are constant size, so the last executed
@@ -897,13 +904,27 @@ static int cs_etm__sample(struct cs_etm_queue *etmq)
 		etmq->period_instructions = instrs_over;
 	}
 
-	if (etm->sample_branches &&
-	    etmq->prev_packet &&
-	    etmq->prev_packet->sample_type == CS_ETM_RANGE &&
-	    etmq->prev_packet->last_instr_taken_branch) {
-		ret = cs_etm__synth_branch_sample(etmq);
-		if (ret)
-			return ret;
+	if (etm->sample_branches && etmq->prev_packet) {
+		bool generate_sample = false;
+
+		/* Generate sample for start tracing packet */
+		if (etmq->prev_packet->sample_type == 0)
+			generate_sample = true;
+
+		/* Generate sample for exception packet */
+		if (etmq->prev_packet->exc == true)
+			generate_sample = true;
+
+		/* Generate sample for normal branch packet */
+		if (etmq->prev_packet->sample_type == CS_ETM_RANGE &&
+		    etmq->prev_packet->last_instr_taken_branch)
+			generate_sample = true;
+
+		if (generate_sample) {
+			ret = cs_etm__synth_branch_sample(etmq);
+			if (ret)
+				return ret;
+		}
 	}
 
 	if (etm->sample_branches || etm->synth_opts.last_branch) {
-- 
2.7.4