perf evsel: Allow evsel__newtp without libtraceevent

Switch from reading the tracepoint format to reading the id directly for
the evsel config. This avoids the need to initialize libtraceevent,
plugins, etc. It is sufficient for many tracepoint commands to work
like:

  $ perf stat -e sched:sched_switch true

To populate evsel->tp_format, do lazy initialization using libtraceevent
in the evsel__tp_format function (the sys and name are saved in
evsel__newtp_idx for this purpose).

Reading the id should be indicative of the format failing to load, but
if not an error is reported in evsel__tp_format. This could happen for a
tracepoint with a format that fails to parse.

As tracepoints can be parsed without libtraceevent with this, remove the
associated #ifdefs in parse-events.c.

By only lazily parsing the tracepoint format information it is hoped
this will help improve the performance of code using tracepoints but not
the format information. It also cuts down on the build and ifdef logic.

Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ben Gainey <ben.gainey@arm.com>
Cc: Colin Ian King <colin.i.king@gmail.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Paran Lee <p4ranlee@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steinar H. Gunderson <sesse@google.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Thomas Falcon <thomas.falcon@intel.com>
Cc: Weilin Wang <weilin.wang@intel.com>
Cc: Yang Jihong <yangjihong@bytedance.com>
Cc: Yang Li <yang.lee@linux.alibaba.com>
Cc: Ze Gao <zegao2021@gmail.com>
Cc: Zixian Cai <fzczx123@gmail.com>
Cc: zhaimingbing <zhaimingbing@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20241118225345.889810-7-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.c

@@ -544,54 +544,101 @@ out_err:
 	return NULL;
 }
 
+static int trace_event__id(const char *sys, const char *name)
+{
+	char *tp_dir = get_events_file(sys);
+	char path[PATH_MAX];
+	int id, err;
+
+	if (!tp_dir)
+		return -1;
+
+	scnprintf(path, PATH_MAX, "%s/%s/id", tp_dir, name);
+	put_events_file(tp_dir);
+	err = filename__read_int(path, &id);
+	if (err)
+		return err;
+
+	return id;
+}
+
 /*
  * Returns pointer with encoded error via <linux/err.h> interface.
  */
-#ifdef HAVE_LIBTRACEEVENT
 struct evsel *evsel__newtp_idx(const char *sys, const char *name, int idx, bool format)
 {
+	struct perf_event_attr attr = {
+		.type	       = PERF_TYPE_TRACEPOINT,
+		.sample_type   = (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
+				PERF_SAMPLE_CPU | PERF_SAMPLE_PERIOD),
+	};
 	struct evsel *evsel = zalloc(perf_evsel__object.size);
-	int err = -ENOMEM;
+	int err = -ENOMEM, id = -1;
 
-	if (evsel == NULL) {
+	if (evsel == NULL)
 		goto out_err;
-	} else {
-		struct perf_event_attr attr = {
-			.type	       = PERF_TYPE_TRACEPOINT,
-			.sample_type   = (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
-					  PERF_SAMPLE_CPU | PERF_SAMPLE_PERIOD),
-		};
 
-		if (asprintf(&evsel->name, "%s:%s", sys, name) < 0)
+
+	if (asprintf(&evsel->name, "%s:%s", sys, name) < 0)
+		goto out_free;
+
+#ifdef HAVE_LIBTRACEEVENT
+	evsel->tp_sys = strdup(sys);
+	if (!evsel->tp_sys)
+		goto out_free;
+
+	evsel->tp_name = strdup(name);
+	if (!evsel->tp_name)
+		goto out_free;
+#endif
+
+	event_attr_init(&attr);
+
+	if (format) {
+		id = trace_event__id(sys, name);
+		if (id < 0) {
+			err = id;
 			goto out_free;
-
-		event_attr_init(&attr);
-
-		if (format) {
-			evsel->tp_format = trace_event__tp_format(sys, name);
-			if (IS_ERR(evsel->tp_format)) {
-				err = PTR_ERR(evsel->tp_format);
-				evsel->tp_format = NULL;
-				goto out_free;
-			}
-			attr.config = evsel->tp_format->id;
-		} else {
-			attr.config = (__u64) -1;
 		}
-
-
-		attr.sample_period = 1;
-		evsel__init(evsel, &attr, idx);
 	}
-
+	attr.config = (__u64)id;
+	attr.sample_period = 1;
+	evsel__init(evsel, &attr, idx);
 	return evsel;
 
 out_free:
 	zfree(&evsel->name);
+#ifdef HAVE_LIBTRACEEVENT
+	zfree(&evsel->tp_sys);
+	zfree(&evsel->tp_name);
+#endif
 	free(evsel);
 out_err:
 	return ERR_PTR(err);
 }
+
+#ifdef HAVE_LIBTRACEEVENT
+struct tep_event *evsel__tp_format(struct evsel *evsel)
+{
+	struct tep_event *tp_format = evsel->tp_format;
+
+	if (tp_format)
+		return tp_format;
+
+	if (evsel->core.attr.type != PERF_TYPE_TRACEPOINT)
+		return NULL;
+
+	tp_format = trace_event__tp_format(evsel->tp_sys, evsel->tp_name);
+	if (IS_ERR(tp_format)) {
+		int err = -PTR_ERR(evsel->tp_format);
+
+		pr_err("Error getting tracepoint format '%s' '%s'(%d)\n",
+			evsel__name(evsel), strerror(err), err);
+		return NULL;
+	}
+	evsel->tp_format = tp_format;
+	return evsel->tp_format;
+}
 #endif
 
 const char *const evsel__hw_names[PERF_COUNT_HW_MAX] = {
@@ -1588,6 +1635,10 @@ void evsel__exit(struct evsel *evsel)
 	perf_thread_map__put(evsel->core.threads);
 	zfree(&evsel->group_name);
 	zfree(&evsel->name);
+#ifdef HAVE_LIBTRACEEVENT
+	zfree(&evsel->tp_sys);
+	zfree(&evsel->tp_name);
+#endif
 	zfree(&evsel->filter);
 	zfree(&evsel->group_pmu_name);
 	zfree(&evsel->unit);

tools/perf/util/evsel.h

@@ -59,6 +59,8 @@ struct evsel {
 		char			*group_name;
 		const char		*group_pmu_name;
 #ifdef HAVE_LIBTRACEEVENT
+		char			*tp_sys;
+		char			*tp_name;
 		struct tep_event	*tp_format;
 #endif
 		char			*filter;
@@ -247,25 +249,17 @@ int copy_config_terms(struct list_head *dst, struct list_head *src);
 void free_config_terms(struct list_head *config_terms);
 
 
-#ifdef HAVE_LIBTRACEEVENT
-struct evsel *evsel__newtp_idx(const char *sys, const char *name, int idx, bool format);
-
 /*
  * Returns pointer with encoded error via <linux/err.h> interface.
  */
+struct evsel *evsel__newtp_idx(const char *sys, const char *name, int idx, bool format);
 static inline struct evsel *evsel__newtp(const char *sys, const char *name)
 {
 	return evsel__newtp_idx(sys, name, 0, true);
 }
 
-static inline struct tep_event *evsel__tp_format(struct evsel *evsel)
-{
-	return evsel->tp_format;
-}
-#endif
-
 #ifdef HAVE_LIBTRACEEVENT
-struct tep_event *event_format__new(const char *sys, const char *name);
+struct tep_event *evsel__tp_format(struct evsel *evsel);
 #endif
 
 void evsel__init(struct evsel *evsel, struct perf_event_attr *attr, int idx);

tools/perf/util/parse-events.c

@@ -489,7 +489,6 @@ int parse_events_add_cache(struct list_head *list, int *idx, const char *name,
 	return found_supported ? 0 : -EINVAL;
 }
 
-#ifdef HAVE_LIBTRACEEVENT
 static void tracepoint_error(struct parse_events_error *e, int err,
 			     const char *sys, const char *name, int column)
 {
@@ -644,7 +643,6 @@ static int add_tracepoint_multi_sys(struct parse_events_state *parse_state,
 	closedir(events_dir);
 	return ret;
 }
-#endif /* HAVE_LIBTRACEEVENT */
 
 size_t default_breakpoint_len(void)
 {
@@ -1066,7 +1064,6 @@ static int config_term_pmu(struct perf_event_attr *attr,
 	return config_term_common(attr, term, err);
 }
 
-#ifdef HAVE_LIBTRACEEVENT
 static int config_term_tracepoint(struct perf_event_attr *attr,
 				  struct parse_events_term *term,
 				  struct parse_events_error *err)
@@ -1111,7 +1108,6 @@ static int config_term_tracepoint(struct perf_event_attr *attr,
 
 	return 0;
 }
-#endif
 
 static int config_attr(struct perf_event_attr *attr,
 		       const struct parse_events_terms *head,
@@ -1303,7 +1299,7 @@ int parse_events_add_tracepoint(struct parse_events_state *parse_state,
 				struct parse_events_terms *head_config, void *loc_)
 {
 	YYLTYPE *loc = loc_;
-#ifdef HAVE_LIBTRACEEVENT
+
 	if (head_config) {
 		struct perf_event_attr attr;
 
@@ -1318,16 +1314,6 @@ int parse_events_add_tracepoint(struct parse_events_state *parse_state,
 	else
 		return add_tracepoint_event(parse_state, list, sys, event,
 					    err, head_config, loc);
-#else
-	(void)parse_state;
-	(void)list;
-	(void)sys;
-	(void)event;
-	(void)head_config;
-	parse_events_error__handle(err, loc->first_column, strdup("unsupported tracepoint"),
-				strdup("libtraceevent is necessary for tracepoint support"));
-	return -1;
-#endif
 }
 
 static int __parse_events_add_numeric(struct parse_events_state *parse_state,