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>

1 files changed, 77 insertions, 26 deletions

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 4759d644a5aa2..6cffba96477ee 100644
--- a/tools/perf/util/evsel.c
+++ b/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)
-			goto out_free;
 
-		event_attr_init(&attr);
+	if (asprintf(&evsel->name, "%s:%s", sys, name) < 0)
+		goto out_free;
 
-		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;
-		}
+#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
 
-		attr.sample_period = 1;
-		evsel__init(evsel, &attr, idx);
-	}
+	event_attr_init(&attr);
 
+	if (format) {
+		id = trace_event__id(sys, name);
+		if (id < 0) {
+			err = id;
+			goto out_free;
+		}
+	}
+	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);