linux-kernel - [PATCH 3/8] perf cs-etm: Remove cs_etm_

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Message-Id: <20240905105043.160225-4-james.clark@linaro.org>
Date: Thu,  5 Sep 2024 11:50:34 +0100
From: James Clark <james.clark@...aro.org>
To: linux-perf-users@...r.kernel.org,
	gankulkarni@...amperecomputing.com,
	coresight@...ts.linaro.org,
	leo.yan@....com,
	scclevenger@...amperecomputing.com
Cc: James Clark <james.clark@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	John Garry <john.g.garry@...cle.com>,
	Will Deacon <will@...nel.org>,
	Leo Yan <leo.yan@...ux.dev>,
	Ben Gainey <ben.gainey@....com>,
	Ruidong Tian <tianruidong@...ux.alibaba.com>,
	Benjamin Gray <bgray@...ux.ibm.com>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 3/8] perf cs-etm: Remove cs_etm__flush()

This is only called on a discontinuity, and it generates a normal
sample and then clears the branch buffer. I'm not convinced that any
of the subtle differences between cs_etm__flush() and cs_etm__sample()
weren't actual bugs or potential sources of them.

Replace it with a call to the existing sample function and then a clear
of the branch buffer.

One obvious difference is that it now generates a range of instructions
based on instructions_sample_period, rather than only a single
instruction sample. I think this is actually the correct thing to do.

Signed-off-by: James Clark <james.clark@...aro.org>
---
 tools/perf/util/cs-etm.c | 62 ++++------------------------------------
 1 file changed, 5 insertions(+), 57 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 602e791ff5ba..cdda8403af2b 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -1908,60 +1908,6 @@ static int cs_etm__exception(struct cs_etm_traceid_queue *tidq)
 	return 0;
 }
 
-static int cs_etm__flush(struct cs_etm_queue *etmq,
-			 struct cs_etm_traceid_queue *tidq)
-{
-	int err = 0;
-	struct cs_etm_auxtrace *etm = etmq->etm;
-
-	/* Handle start tracing packet */
-	if (tidq->prev_packet->sample_type == CS_ETM_EMPTY)
-		goto swap_packet;
-
-	if (etmq->etm->synth_opts.last_branch &&
-	    etmq->etm->synth_opts.instructions &&
-	    tidq->prev_packet->sample_type == CS_ETM_RANGE) {
-		u64 addr;
-
-		/* Prepare last branches for instruction sample */
-		cs_etm__copy_last_branch_rb(etmq, tidq);
-
-		/*
-		 * Generate a last branch event for the branches left in the
-		 * circular buffer at the end of the trace.
-		 *
-		 * Use the address of the end of the last reported execution
-		 * range
-		 */
-		addr = cs_etm__last_executed_instr(tidq->prev_packet);
-
-		err = cs_etm__synth_instruction_sample(
-			etmq, tidq, addr,
-			tidq->period_instructions);
-		if (err)
-			return err;
-
-		tidq->period_instructions = 0;
-
-	}
-
-	if (etm->synth_opts.branches &&
-	    tidq->prev_packet->sample_type == CS_ETM_RANGE) {
-		err = cs_etm__synth_branch_sample(etmq, tidq);
-		if (err)
-			return err;
-	}
-
-swap_packet:
-	cs_etm__packet_swap(etm, tidq);
-
-	/* Reset last branches after flush the trace */
-	if (etm->synth_opts.last_branch)
-		cs_etm__reset_last_branch_rb(tidq);
-
-	return err;
-}
-
 static int cs_etm__end_block(struct cs_etm_queue *etmq,
 			     struct cs_etm_traceid_queue *tidq)
 {
@@ -2457,10 +2403,12 @@ static int cs_etm__process_traceid_queue(struct cs_etm_queue *etmq,
 			break;
 		case CS_ETM_DISCONTINUITY:
 			/*
-			 * Discontinuity in trace, flush
-			 * previous branch stack
+			 * Discontinuity in trace, generate a sample then
+			 * clear the branch stack.
 			 */
-			cs_etm__flush(etmq, tidq);
+			cs_etm__sample(etmq, tidq);
+			if (etmq->etm->synth_opts.last_branch)
+				cs_etm__reset_last_branch_rb(tidq);
 			break;
 		case CS_ETM_EMPTY:
 			/*
-- 
2.34.1