linux-kernel - [PATCH v1 05/22] perf metricgroup: Add care to picking the evsel for displaying a metric

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251024175857.808401-6-irogers@google.com>
Date: Fri, 24 Oct 2025 10:58:40 -0700
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>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	James Clark <james.clark@...aro.org>, Xu Yang <xu.yang_2@....com>, 
	Chun-Tse Shao <ctshao@...gle.com>, Thomas Richter <tmricht@...ux.ibm.com>, 
	Sumanth Korikkar <sumanthk@...ux.ibm.com>, Collin Funk <collin.funk1@...il.com>, 
	Thomas Falcon <thomas.falcon@...el.com>, Howard Chu <howardchu95@...il.com>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>, Levi Yun <yeoreum.yun@....com>, 
	Yang Li <yang.lee@...ux.alibaba.com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org
Subject: [PATCH v1 05/22] perf metricgroup: Add care to picking the evsel for
 displaying a metric

Rather than using the first evsel in the matched events, try to find
the least shared non-tool evsel. The aim is to pick the first evsel
that typifies the metric within the list of metrics.

This addresses an issue where Default metric group metrics may lose
their counter value due to how the stat displaying hides counters for
default event/metric output.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/metricgroup.c | 48 ++++++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index 48936e517803..76092ee26761 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -1323,6 +1323,51 @@ static int parse_ids(bool metric_no_merge, bool fake_pmu,
 	return ret;
 }
 
+/* How many times will a given evsel be used in a set of metrics? */
+static int count_uses(struct list_head *metric_list, struct evsel *evsel)
+{
+	const char *metric_id = evsel__metric_id(evsel);
+	struct metric *m;
+	int uses = 0;
+
+	list_for_each_entry(m, metric_list, nd) {
+		if (hashmap__find(m->pctx->ids, metric_id, NULL))
+			uses++;
+	}
+	return uses;
+}
+
+/*
+ * Select the evsel that stat-display will use to trigger shadow/metric
+ * printing. Pick the least shared non-tool evsel, encouraging metrics to be
+ * with a hardware counter that is specific to them.
+ */
+static struct evsel *pick_display_evsel(struct list_head *metric_list,
+					struct evsel **metric_events)
+{
+	struct evsel *selected = metric_events[0];
+	size_t selected_uses;
+	bool selected_is_tool;
+
+	if (!selected)
+		return NULL;
+
+	selected_uses = count_uses(metric_list, selected);
+	selected_is_tool = evsel__is_tool(selected);
+	for (int i = 1; metric_events[i]; i++) {
+		struct evsel *candidate = metric_events[i];
+		size_t candidate_uses = count_uses(metric_list, candidate);
+
+		if ((selected_is_tool && !evsel__is_tool(candidate)) ||
+		    (candidate_uses < selected_uses)) {
+			selected = candidate;
+			selected_uses = candidate_uses;
+			selected_is_tool = evsel__is_tool(selected);
+		}
+	}
+	return selected;
+}
+
 static int parse_groups(struct evlist *perf_evlist,
 			const char *pmu, const char *str,
 			bool metric_no_group,
@@ -1430,7 +1475,8 @@ static int parse_groups(struct evlist *perf_evlist,
 			goto out;
 		}
 
-		me = metricgroup__lookup(&perf_evlist->metric_events, metric_events[0],
+		me = metricgroup__lookup(&perf_evlist->metric_events,
+					 pick_display_evsel(&metric_list, metric_events),
 					 /*create=*/true);
 
 		expr = malloc(sizeof(struct metric_expr));
-- 
2.51.1.821.gb6fe4d2222-goog