linux-kernel - [PATCH v2 1/4] perf parse-events: Avoid scanning PMUs that can't contain events

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Message-ID: <20250326035045.129440-2-irogers@google.com>
Date: Tue, 25 Mar 2025 20:50:42 -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>, 
	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>, 
	"Masami Hiramatsu (Google)" <mhiramat@...nel.org>, James Clark <james.clark@...aro.org>, 
	Weilin Wang <weilin.wang@...el.com>, Dominique Martinet <asmadeus@...ewreck.org>, 
	Thomas Richter <tmricht@...ux.ibm.com>, Junhao He <hejunhao3@...wei.com>, 
	Jean-Philippe Romain <jean-philippe.romain@...s.st.com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org
Cc: dri-devel@...ts.freedesktop.org
Subject: [PATCH v2 1/4] perf parse-events: Avoid scanning PMUs that can't
 contain events

Add perf_pmus__scan_for_event that only reads sysfs for pmus that
could contain a given event.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/parse-events.c |  4 ++--
 tools/perf/util/pmus.c         | 35 ++++++++++++++++++++++++++++++++++
 tools/perf/util/pmus.h         |  1 +
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 5152fd5a6ead..d77af1d24985 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -434,7 +434,7 @@ int parse_events_add_cache(struct list_head *list, int *idx, const char *name,
 	const char *config_name = get_config_name(parsed_terms);
 	const char *metric_id = get_config_metric_id(parsed_terms);
 
-	while ((pmu = perf_pmus__scan(pmu)) != NULL) {
+	while ((pmu = perf_pmus__scan_for_event(pmu, name)) != NULL) {
 		LIST_HEAD(config_terms);
 		struct perf_event_attr attr;
 		int ret;
@@ -1585,7 +1585,7 @@ int parse_events_multi_pmu_add(struct parse_events_state *parse_state,
 
 	INIT_LIST_HEAD(list);
 
-	while ((pmu = perf_pmus__scan(pmu)) != NULL) {
+	while ((pmu = perf_pmus__scan_for_event(pmu, event_name)) != NULL) {
 		bool auto_merge_stats;
 
 		if (parse_events__filter_pmu(parse_state, pmu))
diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
index b99292de7669..f2706c395509 100644
--- a/tools/perf/util/pmus.c
+++ b/tools/perf/util/pmus.c
@@ -350,6 +350,41 @@ struct perf_pmu *perf_pmus__scan_core(struct perf_pmu *pmu)
 	return NULL;
 }
 
+struct perf_pmu *perf_pmus__scan_for_event(struct perf_pmu *pmu, const char *event)
+{
+	bool use_core_pmus = !pmu || pmu->is_core;
+
+	if (!pmu) {
+		/* Hwmon filename values that aren't used. */
+		enum hwmon_type type;
+		int number;
+		/*
+		 * Core PMUs, other sysfs PMUs and tool PMU can take all event
+		 * types or aren't wother optimizing for.
+		 */
+		unsigned int to_read_pmus =  PERF_TOOL_PMU_TYPE_PE_CORE_MASK |
+			PERF_TOOL_PMU_TYPE_PE_OTHER_MASK |
+			PERF_TOOL_PMU_TYPE_TOOL_MASK;
+
+		/* Could the event be a hwmon event? */
+		if (parse_hwmon_filename(event, &type, &number, /*item=*/NULL, /*alarm=*/NULL))
+			to_read_pmus |= PERF_TOOL_PMU_TYPE_HWMON_MASK;
+
+		pmu_read_sysfs(to_read_pmus);
+		pmu = list_prepare_entry(pmu, &core_pmus, list);
+	}
+	if (use_core_pmus) {
+		list_for_each_entry_continue(pmu, &core_pmus, list)
+			return pmu;
+
+		pmu = NULL;
+		pmu = list_prepare_entry(pmu, &other_pmus, list);
+	}
+	list_for_each_entry_continue(pmu, &other_pmus, list)
+		return pmu;
+	return NULL;
+}
+
 static struct perf_pmu *perf_pmus__scan_skip_duplicates(struct perf_pmu *pmu)
 {
 	bool use_core_pmus = !pmu || pmu->is_core;
diff --git a/tools/perf/util/pmus.h b/tools/perf/util/pmus.h
index 8def20e615ad..213ee65306d6 100644
--- a/tools/perf/util/pmus.h
+++ b/tools/perf/util/pmus.h
@@ -19,6 +19,7 @@ struct perf_pmu *perf_pmus__find_by_type(unsigned int type);
 
 struct perf_pmu *perf_pmus__scan(struct perf_pmu *pmu);
 struct perf_pmu *perf_pmus__scan_core(struct perf_pmu *pmu);
+struct perf_pmu *perf_pmus__scan_for_event(struct perf_pmu *pmu, const char *event);
 
 const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str);
 
-- 
2.49.0.395.g12beb8f557-goog