linux-kernel - [PATCH v1 2/3] perf arm-spe: Correct sample flags for dummy event

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Date:   Thu, 29 Apr 2021 23:00:59 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        James Clark <James.Clark@....com>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....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-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Al Grant <Al.Grant@....com>
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v1 2/3] perf arm-spe: Correct sample flags for dummy event

The dummy event is mainly used for mmap, the TIME sample is only needed
for per-cpu case so that the perf tool can rely on the correct timing
for parsing symbols.  And the CPU sample is useless for mmap.

This patch enables TIME sample for per-cpu mmap and doesn't enable CPU
sample.  For later extension (e.g. support multiple AUX events), it sets
the dummy event when the condition "opts->full_auxtrace" is true.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 tools/perf/arch/arm64/util/arm-spe.c | 30 ++++++++++++++++------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c
index 902e73a64184..f6eec0900604 100644
--- a/tools/perf/arch/arm64/util/arm-spe.c
+++ b/tools/perf/arch/arm64/util/arm-spe.c
@@ -70,7 +70,6 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
 	struct evsel *evsel, *arm_spe_evsel = NULL;
 	struct perf_cpu_map *cpus = evlist->core.cpus;
 	bool privileged = perf_event_paranoid_check(-1);
-	struct evsel *tracking_evsel;
 	int err;
 
 	sper->evlist = evlist;
@@ -126,18 +125,23 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
 		evsel__set_sample_bit(arm_spe_evsel, CPU);
 
 	/* Add dummy event to keep tracking */
-	err = parse_events(evlist, "dummy:u", NULL);
-	if (err)
-		return err;
-
-	tracking_evsel = evlist__last(evlist);
-	evlist__set_tracking_event(evlist, tracking_evsel);
-
-	tracking_evsel->core.attr.freq = 0;
-	tracking_evsel->core.attr.sample_period = 1;
-	evsel__set_sample_bit(tracking_evsel, TIME);
-	evsel__set_sample_bit(tracking_evsel, CPU);
-	evsel__reset_sample_bit(tracking_evsel, BRANCH_STACK);
+	if (opts->full_auxtrace) {
+		struct evsel *tracking_evsel;
+
+		err = parse_events(evlist, "dummy:u", NULL);
+		if (err)
+			return err;
+
+		tracking_evsel = evlist__last(evlist);
+		evlist__set_tracking_event(evlist, tracking_evsel);
+
+		tracking_evsel->core.attr.freq = 0;
+		tracking_evsel->core.attr.sample_period = 1;
+
+		/* In per-cpu case, always need the time of mmap events etc */
+		if (!perf_cpu_map__empty(cpus))
+			evsel__set_sample_bit(tracking_evsel, TIME);
+	}
 
 	return 0;
 }
-- 
2.25.1