perf intel-tpebs: Separate evsel__tpebs_prepare() out of evsel__tpebs_open()

Separate the creation of the tpebs_retire_lat result out of the opening
step.

This is in preparation for adding a prepare operation for evlists.

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Weilin Wang <weilin.wang@intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Andreas Färber <afaerber@suse.de>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Falcon <thomas.falcon@intel.com>
Link: https://lore.kernel.org/r/20250414174134.3095492-5-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 86 insertions, 47 deletions

diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c
index 566e0ddcad88..2186818b2c9b 100644
--- a/tools/perf/util/intel-tpebs.c
+++ b/tools/perf/util/intel-tpebs.c
@@ -37,7 +37,7 @@ static struct child_process tpebs_cmd;
 struct tpebs_retire_lat {
 	struct list_head nd;
 	/* Event name */
-	const char *name;
+	char *name;
 	/* Event name with the TPEBS modifier R */
 	const char *tpebs_name;
 	/* Count of retire_latency values found in sample data */
@@ -190,6 +190,82 @@ static int tpebs_stop(void)
 	return ret;
 }
 
+static char *evsel__tpebs_name(struct evsel *evsel)
+{
+	char *name, *modifier;
+
+	name = strdup(evsel->name);
+	if (!name)
+		return NULL;
+
+	modifier = strrchr(name, 'R');
+	if (!modifier) {
+		pr_err("Tpebs event missing modifier '%s'\n", name);
+		free(name);
+		return NULL;
+	}
+
+	*modifier = 'p';
+	return name;
+}
+
+static struct tpebs_retire_lat *tpebs_retire_lat__new(struct evsel *evsel)
+{
+	struct tpebs_retire_lat *result = zalloc(sizeof(*result));
+
+	if (!result)
+		return NULL;
+
+	result->tpebs_name = evsel->name;
+	result->name = evsel__tpebs_name(evsel);
+	if (!result->name) {
+		free(result);
+		return NULL;
+	}
+	list_add_tail(&result->nd, &tpebs_results);
+	tpebs_event_size++;
+	return result;
+}
+
+/**
+ * evsel__tpebs_prepare - create tpebs data structures ready for opening.
+ * @evsel: retire_latency evsel, all evsels on its list will be prepared.
+ */
+static int evsel__tpebs_prepare(struct evsel *evsel)
+{
+	struct evsel *pos;
+	struct tpebs_retire_lat *tpebs_event;
+
+	list_for_each_entry(tpebs_event, &tpebs_results, nd) {
+		if (!strcmp(tpebs_event->tpebs_name, evsel->name)) {
+			/*
+			 * evsel, or an identically named one, was already
+			 * prepared.
+			 */
+			return 0;
+		}
+	}
+	tpebs_event = tpebs_retire_lat__new(evsel);
+	if (!tpebs_event)
+		return -ENOMEM;
+
+	/*
+	 * Eagerly prepare all other evsels on the list to try to ensure that by
+	 * open they are all known.
+	 */
+	evlist__for_each_entry(evsel->evlist, pos) {
+		int ret;
+
+		if (pos == evsel || !pos->retire_lat)
+			continue;
+
+		ret = evsel__tpebs_prepare(pos);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
 /**
  * evsel__tpebs_open - starts tpebs execution.
  * @evsel: retire_latency evsel, all evsels on its list will be selected. Each
@@ -197,10 +273,7 @@ static int tpebs_stop(void)
  */
 int evsel__tpebs_open(struct evsel *evsel)
 {
-	int ret = 0;
-	struct evsel *pos;
-	struct evlist *evsel_list = evsel->evlist;
-	char cpumap_buf[50];
+	int ret;
 
 	/*
 	 * We should only run tpebs_start when tpebs_recording is enabled.
@@ -209,49 +282,13 @@ int evsel__tpebs_open(struct evsel *evsel)
 	if (tpebs_cmd.pid != 0 || !tpebs_recording)
 		return 0;
 
-	cpu_map__snprint(evsel_list->core.user_requested_cpus, cpumap_buf, sizeof(cpumap_buf));
-	/*
-	 * Prepare perf record for sampling event retire_latency before fork and
-	 * prepare workload
-	 */
-	evlist__for_each_entry(evsel_list, pos) {
-		int i;
-		char *name;
-		struct tpebs_retire_lat *new;
-
-		if (!pos->retire_lat)
-			continue;
-
-		pr_debug("tpebs: Retire_latency of event %s is required\n", pos->name);
-		for (i = strlen(pos->name) - 1; i > 0; i--) {
-			if (pos->name[i] == 'R')
-				break;
-		}
-		if (i <= 0 || pos->name[i] != 'R') {
-			ret = -1;
-			goto err;
-		}
-
-		name = strdup(pos->name);
-		if (!name) {
-			ret = -ENOMEM;
-			goto err;
-		}
-		name[i] = 'p';
-
-		new = zalloc(sizeof(*new));
-		if (!new) {
-			ret = -1;
-			zfree(&name);
-			goto err;
-		}
-		new->name = name;
-		new->tpebs_name = pos->name;
-		list_add_tail(&new->nd, &tpebs_results);
-		tpebs_event_size += 1;
-	}
+	ret = evsel__tpebs_prepare(evsel);
+	if (ret)
+		return ret;
 
 	if (tpebs_event_size > 0) {
+		struct evlist *evsel_list = evsel->evlist;
+		char cpumap_buf[50];
 		struct pollfd pollfd = { .events = POLLIN, };
 		int control_fd[2], ack_fd[2], len;
 		char ack_buf[8];
@@ -268,6 +305,9 @@ int evsel__tpebs_open(struct evsel *evsel)
 			goto out;
 		}
 
+		cpu_map__snprint(evsel_list->core.user_requested_cpus, cpumap_buf,
+				 sizeof(cpumap_buf));
+
 		ret = start_perf_record(control_fd, ack_fd, cpumap_buf);
 		if (ret)
 			goto out;
@@ -321,7 +361,6 @@ out:
 		close(ack_fd[0]);
 		close(ack_fd[1]);
 	}
-err:
 	if (ret)
 		tpebs_delete();
 	return ret;