perf pmu: Be lazy about loading event info files from sysfs

Event info is only needed when an event is parsed or when merging data
from an JSON and sysfs event. Be lazy in its loading to reduce file
accesses.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Gaosheng Cui <cuigaosheng1@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230824041330.266337-16-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: captain5050

tools/perf/util/pmu.c

@@ -58,6 +58,11 @@ struct perf_pmu_alias {
 	struct list_head terms;
 	/** @list: List element of struct perf_pmu aliases. */
 	struct list_head list;
+	/**
+	 * @pmu_name: The name copied from the json struct pmu_event. This can
+	 * differ from the PMU name as it won't have suffixes.
+	 */
+	char *pmu_name;
 	/** @unit: Units for the event, such as bytes or cache lines. */
 	char unit[UNIT_MAX_LEN+1];
 	/** @scale: Value to scale read counter values by. */
@@ -79,11 +84,10 @@ struct perf_pmu_alias {
 	 * default.
 	 */
 	bool deprecated;
-	/**
-	 * @pmu_name: The name copied from the json struct pmu_event. This can
-	 * differ from the PMU name as it won't have suffixes.
-	 */
-	char *pmu_name;
+	/** @from_sysfs: Was the alias from sysfs or a json event? */
+	bool from_sysfs;
+	/** @info_loaded: Have the scale, unit and other values been read from disk? */
+	bool info_loaded;
 };
 
 /**
@@ -280,17 +284,21 @@ int perf_pmu__convert_scale(const char *scale, char **end, double *sval)
 	return ret;
 }
 
-static int perf_pmu__parse_scale(struct perf_pmu_alias *alias, int dirfd, const char *name)
+static int perf_pmu__parse_scale(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
 {
 	struct stat st;
 	ssize_t sret;
+	size_t len;
 	char scale[128];
 	int fd, ret = -1;
 	char path[PATH_MAX];
 
-	scnprintf(path, PATH_MAX, "%s.scale", name);
+	len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
+	if (!len)
+		return 0;
+	scnprintf(path + len, sizeof(path) - len, "%s/%s.scale", pmu->name, alias->name);
 
-	fd = openat(dirfd, path, O_RDONLY);
+	fd = open(path, O_RDONLY);
 	if (fd == -1)
 		return -1;
 
@@ -312,15 +320,20 @@ static int perf_pmu__parse_scale(struct perf_pmu_alias *alias, int dirfd, const
 	return ret;
 }
 
-static int perf_pmu__parse_unit(struct perf_pmu_alias *alias, int dirfd, const char *name)
+static int perf_pmu__parse_unit(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
 {
 	char path[PATH_MAX];
+	size_t len;
 	ssize_t sret;
 	int fd;
 
-	scnprintf(path, PATH_MAX, "%s.unit", name);
 
-	fd = openat(dirfd, path, O_RDONLY);
+	len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
+	if (!len)
+		return 0;
+	scnprintf(path + len, sizeof(path) - len, "%s/%s.unit", pmu->name, alias->name);
+
+	fd = open(path, O_RDONLY);
 	if (fd == -1)
 		return -1;
 
@@ -343,14 +356,18 @@ static int perf_pmu__parse_unit(struct perf_pmu_alias *alias, int dirfd, const c
 }
 
 static int
-perf_pmu__parse_per_pkg(struct perf_pmu_alias *alias, int dirfd, const char *name)
+perf_pmu__parse_per_pkg(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
 {
 	char path[PATH_MAX];
+	size_t len;
 	int fd;
 
-	scnprintf(path, PATH_MAX, "%s.per-pkg", name);
+	len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
+	if (!len)
+		return 0;
+	scnprintf(path + len, sizeof(path) - len, "%s/%s.per-pkg", pmu->name, alias->name);
 
-	fd = openat(dirfd, path, O_RDONLY);
+	fd = open(path, O_RDONLY);
 	if (fd == -1)
 		return -1;
 
@@ -360,15 +377,18 @@ perf_pmu__parse_per_pkg(struct perf_pmu_alias *alias, int dirfd, const char *nam
 	return 0;
 }
 
-static int perf_pmu__parse_snapshot(struct perf_pmu_alias *alias,
-				    int dirfd, const char *name)
+static int perf_pmu__parse_snapshot(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
 {
 	char path[PATH_MAX];
+	size_t len;
 	int fd;
 
-	scnprintf(path, PATH_MAX, "%s.snapshot", name);
+	len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
+	if (!len)
+		return 0;
+	scnprintf(path + len, sizeof(path) - len, "%s/%s.snapshot", pmu->name, alias->name);
 
-	fd = openat(dirfd, path, O_RDONLY);
+	fd = open(path, O_RDONLY);
 	if (fd == -1)
 		return -1;
 
@@ -429,32 +449,52 @@ static bool assign_str(const char *name, const char *field, char **old_str,
 	return true;
 }
 
+static void read_alias_info(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
+{
+	if (!alias->from_sysfs || alias->info_loaded)
+		return;
+
+	/*
+	 * load unit name and scale if available
+	 */
+	perf_pmu__parse_unit(pmu, alias);
+	perf_pmu__parse_scale(pmu, alias);
+	perf_pmu__parse_per_pkg(pmu, alias);
+	perf_pmu__parse_snapshot(pmu, alias);
+}
+
+struct update_alias_data {
+	struct perf_pmu *pmu;
+	struct perf_pmu_alias *alias;
+};
+
 static int update_alias(const struct pmu_event *pe,
 			const struct pmu_events_table *table __maybe_unused,
 			void *vdata)
 {
-	struct perf_pmu_alias *alias = vdata;
+	struct update_alias_data *data = vdata;
 	int ret = 0;
 
-	assign_str(pe->name, "desc", &alias->desc, pe->desc);
-	assign_str(pe->name, "long_desc", &alias->long_desc, pe->long_desc);
-	assign_str(pe->name, "topic", &alias->topic, pe->topic);
-	alias->per_pkg = pe->perpkg;
-	if (assign_str(pe->name, "value", &alias->str, pe->event)) {
-		parse_events_terms__purge(&alias->terms);
-		ret = parse_events_terms(&alias->terms, pe->event, /*input=*/NULL);
+	read_alias_info(data->pmu, data->alias);
+	assign_str(pe->name, "desc", &data->alias->desc, pe->desc);
+	assign_str(pe->name, "long_desc", &data->alias->long_desc, pe->long_desc);
+	assign_str(pe->name, "topic", &data->alias->topic, pe->topic);
+	data->alias->per_pkg = pe->perpkg;
+	if (assign_str(pe->name, "value", &data->alias->str, pe->event)) {
+		parse_events_terms__purge(&data->alias->terms);
+		ret = parse_events_terms(&data->alias->terms, pe->event, /*input=*/NULL);
 	}
 	if (!ret && pe->unit) {
 		char *unit;
 
-		ret = perf_pmu__convert_scale(pe->unit, &unit, &alias->scale);
+		ret = perf_pmu__convert_scale(pe->unit, &unit, &data->alias->scale);
 		if (!ret)
-			snprintf(alias->unit, sizeof(alias->unit), "%s", unit);
+			snprintf(data->alias->unit, sizeof(data->alias->unit), "%s", unit);
 	}
 	return ret;
 }
 
-static int perf_pmu__new_alias(struct perf_pmu *pmu, int dirfd, const char *name,
+static int perf_pmu__new_alias(struct perf_pmu *pmu, const char *name,
 				const char *desc, const char *val, FILE *val_fd,
 				const struct pmu_event *pe)
 {
@@ -498,16 +538,6 @@ static int perf_pmu__new_alias(struct perf_pmu *pmu, int dirfd, const char *name
 	}
 
 	alias->name = strdup(name);
-	if (dirfd >= 0) {
-		/*
-		 * load unit name and scale if available
-		 */
-		perf_pmu__parse_unit(alias, dirfd, name);
-		perf_pmu__parse_scale(alias, dirfd, name);
-		perf_pmu__parse_per_pkg(alias, dirfd, name);
-		perf_pmu__parse_snapshot(alias, dirfd, name);
-	}
-
 	alias->desc = desc ? strdup(desc) : NULL;
 	alias->long_desc = long_desc ? strdup(long_desc) :
 				desc ? strdup(desc) : NULL;
@@ -522,9 +552,15 @@ static int perf_pmu__new_alias(struct perf_pmu *pmu, int dirfd, const char *name
 	}
 	if (!pe) {
 		/* Update an event from sysfs with json data. */
+		struct update_alias_data data = {
+			.pmu = pmu,
+			.alias = alias,
+		};
+
+		alias->from_sysfs = true;
 		if (pmu->events_table) {
 			if (pmu_events_table__find_event(pmu->events_table, pmu, name,
-							 update_alias, alias) == 0)
+							 update_alias, &data) == 0)
 				pmu->loaded_json_aliases++;
 		}
 	}
@@ -612,7 +648,7 @@ static int pmu_aliases_parse(struct perf_pmu *pmu, int dirfd)
 			continue;
 		}
 
-		if (perf_pmu__new_alias(pmu, dirfd, name, /*desc=*/ NULL,
+		if (perf_pmu__new_alias(pmu, name, /*desc=*/ NULL,
 					/*val=*/ NULL, file, /*pe=*/ NULL) < 0)
 			pr_debug("Cannot set up %s\n", name);
 		fclose(file);
@@ -865,7 +901,7 @@ static int pmu_add_cpu_aliases_map_callback(const struct pmu_event *pe,
 {
 	struct perf_pmu *pmu = vdata;
 
-	perf_pmu__new_alias(pmu, -1, pe->name, pe->desc, pe->event, /*val_fd=*/ NULL, pe);
+	perf_pmu__new_alias(pmu, pe->name, pe->desc, pe->event, /*val_fd=*/ NULL, pe);
 	return 0;
 }
 
@@ -901,7 +937,7 @@ static int pmu_add_sys_aliases_iter_fn(const struct pmu_event *pe,
 
 	if (!strcmp(pmu->id, pe->compat) &&
 	    pmu_uncore_alias_match(pe->pmu, pmu->name)) {
-		perf_pmu__new_alias(pmu, -1,
+		perf_pmu__new_alias(pmu,
 				pe->name,
 				pe->desc,
 				pe->event,
@@ -1417,11 +1453,13 @@ static struct perf_pmu_alias *pmu_find_alias(struct perf_pmu *pmu,
 }
 
 
-static int check_info_data(struct perf_pmu_alias *alias,
+static int check_info_data(struct perf_pmu *pmu,
+			   struct perf_pmu_alias *alias,
 			   struct perf_pmu_info *info,
 			   struct parse_events_error *err,
 			   int column)
 {
+	read_alias_info(pmu, alias);
 	/*
 	 * Only one term in event definition can
 	 * define unit, scale and snapshot, fail
@@ -1491,7 +1529,7 @@ int perf_pmu__check_alias(struct perf_pmu *pmu, struct list_head *head_terms,
 			return ret;
 		}
 
-		ret = check_info_data(alias, info, err, term->err_term);
+		ret = check_info_data(pmu, alias, info, err, term->err_term);
 		if (ret)
 			return ret;