linux-kernel - [PATCH v4 2/4] perf stat: Use counter cpumask to skip zero values

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Message-Id: <20250108053428.1724490-3-irogers@google.com>
Date: Tue,  7 Jan 2025 21:34:26 -0800
From: Ian Rogers <irogers@...gle.com>
To: 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>, 
	Kan Liang <kan.liang@...ux.intel.com>, Leo Yan <leo.yan@....com>, 
	Yoshihiro Furudera <fj5100bi@...itsu.com>, Weilin Wang <weilin.wang@...el.com>, 
	Andi Kleen <ak@...ux.intel.com>, James Clark <james.clark@...aro.org>, 
	Dominique Martinet <asmadeus@...ewreck.org>, Yicong Yang <yangyicong@...ilicon.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 2/4] perf stat: Use counter cpumask to skip zero values

When a counter is 0 it may or may not be skipped. For uncore counters
it is common they are only valid on 1 logical CPU and all other CPUs
should be skipped. The PMU's cpumask was used for the skip
calculation, but that cpumask may not reflect user
overrides. Similarly a counter on a core PMU may explicitly not
request a CPU be gathered. If the counter on this CPU's value is 0
then the counter should be skipped as it wasn't requested. Switch from
using the PMU cpumask to that associated with the evsel to support
these cases.

Avoid potential crash with --per-thread mode where config->aggr_get_id
is NULL. Add some examples for the tool event 0 counter skipping.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/stat-display.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index ba79f73e1cf5..32badf623267 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -1042,8 +1042,16 @@ static bool should_skip_zero_counter(struct perf_stat_config *config,
 		return true;
 
 	/*
-	 * Many tool events are only gathered on the first index, skip other
-	 * zero values.
+	 * In per-thread mode the aggr_map and aggr_get_id functions may be
+	 * NULL, assume all 0 values should be output in that case.
+	 */
+	if (!config->aggr_map || !config->aggr_get_id)
+		return false;
+
+	/*
+	 * Tool events may be gathered on all logical CPUs, for example
+	 * system_time, but for many the first index is the only one used, for
+	 * example num_cores. Don't skip for the first index.
 	 */
 	if (evsel__is_tool(counter)) {
 		struct aggr_cpu_id own_id =
@@ -1051,15 +1059,12 @@ static bool should_skip_zero_counter(struct perf_stat_config *config,
 
 		return !aggr_cpu_id__equal(id, &own_id);
 	}
-
 	/*
-	 * Skip value 0 when it's an uncore event and the given aggr id
-	 * does not belong to the PMU cpumask.
+	 * Skip value 0 when the counter's cpumask doesn't match the given aggr
+	 * id.
 	 */
-	if (!counter->pmu || !counter->pmu->is_uncore)
-		return false;
 
-	perf_cpu_map__for_each_cpu(cpu, idx, counter->pmu->cpus) {
+	perf_cpu_map__for_each_cpu(cpu, idx, counter->core.cpus) {
 		struct aggr_cpu_id own_id = config->aggr_get_id(config, cpu);
 
 		if (aggr_cpu_id__equal(id, &own_id))
-- 
2.47.1.613.gc27f4b7a9f-goog