perf pmu: Restructure print_pmu_events() to avoid memory allocations

Previously print_pmu_events() would compute the values to be printed,
place them in struct sevent, sort them and then print them.

Modify the code so that struct sevent holds just the PMU and event, sort
these and then in the main print loop calculate aliases for names, etc.

This avoids memory allocations for copied values as they are computed
then printed.
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Weilin Wang <weilin.wang@intel.com>
Cc: Xin Gao <gaoxin@cdjrlc.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: http://lore.kernel.org/lkml/20221114210723.2749751-9-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/pmu.c

@@ -1553,8 +1553,8 @@ static int sub_non_neg(int a, int b)
 	return a - b;
 }
 
-static char *format_alias(char *buf, int len, struct perf_pmu *pmu,
-			  struct perf_pmu_alias *alias)
+static char *format_alias(char *buf, int len, const struct perf_pmu *pmu,
+			  const struct perf_pmu_alias *alias)
 {
 	struct parse_events_term *term;
 	int used = snprintf(buf, len, "%s/%s", pmu->name, alias->name);
@@ -1579,51 +1579,67 @@ static char *format_alias(char *buf, int len, struct perf_pmu *pmu,
 	return buf;
 }
 
-static char *format_alias_or(char *buf, int len, struct perf_pmu *pmu,
-			     struct perf_pmu_alias *alias)
+static char *format_alias_or(char *buf, int len, const struct perf_pmu *pmu,
+			     const struct perf_pmu_alias *alias)
 {
 	snprintf(buf, len, "%s OR %s/%s/", alias->name, pmu->name, alias->name);
 	return buf;
 }
 
+/** Struct for ordering events as output in perf list. */
 struct sevent {
-	char *name;
-	char *desc;
-	char *topic;
-	char *str;
-	char *pmu;
-	char *metric_expr;
-	char *metric_name;
-	int is_cpu;
+	/** PMU for event. */
+	const struct perf_pmu *pmu;
+	/**
+	 * Optional event for name, desc, etc. If not present then this is a
+	 * selectable PMU and the event name is shown as "//".
+	 */
+	const struct perf_pmu_alias *event;
+	/** Is the PMU for the CPU? */
+	bool is_cpu;
 };
 
 static int cmp_sevent(const void *a, const void *b)
 {
 	const struct sevent *as = a;
 	const struct sevent *bs = b;
+	const char *a_pmu_name, *b_pmu_name;
+	const char *a_name = "//", *a_desc = NULL, *a_topic = "";
+	const char *b_name = "//", *b_desc = NULL, *b_topic = "";
 	int ret;
 
-	/* Put extra events last */
-	if (!!as->desc != !!bs->desc)
-		return !!as->desc - !!bs->desc;
-	if (as->topic && bs->topic) {
-		int n = strcmp(as->topic, bs->topic);
-
-		if (n)
-			return n;
+	if (as->event) {
+		a_name = as->event->name;
+		a_desc = as->event->desc;
+		a_topic = as->event->topic ?: "";
 	}
+	if (bs->event) {
+		b_name = bs->event->name;
+		b_desc = bs->event->desc;
+		b_topic = bs->event->topic ?: "";
+	}
+	/* Put extra events last. */
+	if (!!a_desc != !!b_desc)
+		return !!a_desc - !!b_desc;
+
+	/* Order by topics. */
+	ret = strcmp(a_topic, b_topic);
+	if (ret)
+		return ret;
 
 	/* Order CPU core events to be first */
 	if (as->is_cpu != bs->is_cpu)
 		return bs->is_cpu - as->is_cpu;
 
-	ret = strcmp(as->name, bs->name);
-	if (!ret) {
-		if (as->pmu && bs->pmu)
-			return strcmp(as->pmu, bs->pmu);
-	}
+	/* Order by PMU name. */
+	a_pmu_name = as->pmu->name ?: "";
+	b_pmu_name = bs->pmu->name ?: "";
+	ret = strcmp(a_pmu_name, b_pmu_name);
+	if (ret)
+		return ret;
 
-	return ret;
+	/* Order by event name. */
+	return strcmp(a_name, b_name);
 }
 
 static void wordwrap(char *s, int start, int max, int corr)
@@ -1655,16 +1671,18 @@ bool is_pmu_core(const char *name)
 static bool pmu_alias_is_duplicate(struct sevent *alias_a,
 				   struct sevent *alias_b)
 {
-	/* Different names -> never duplicates */
-	if (strcmp(alias_a->name, alias_b->name))
-		return false;
+	const char *a_pmu_name, *b_pmu_name;
+	const char *a_name = alias_a->event ? alias_a->event->name : "//";
+	const char *b_name = alias_b->event ? alias_b->event->name : "//";
 
-	/* Don't remove duplicates for hybrid PMUs */
-	if (perf_pmu__is_hybrid(alias_a->pmu) &&
-	    perf_pmu__is_hybrid(alias_b->pmu))
+	/* Different names -> never duplicates */
+	if (strcmp(a_name, b_name))
 		return false;
 
-	return true;
+	/* Don't remove duplicates for different PMUs */
+	a_pmu_name = alias_a->pmu->name ?: "";
+	b_pmu_name = alias_b->pmu->name ?: "";
+	return strcmp(a_pmu_name, b_pmu_name) == 0;
 }
 
 void print_pmu_events(const char *event_glob, bool name_only, bool quiet_flag,
@@ -1690,110 +1708,104 @@ void print_pmu_events(const char *event_glob, bool name_only, bool quiet_flag,
 			len++;
 	}
 	aliases = zalloc(sizeof(struct sevent) * len);
-	if (!aliases)
-		goto out_enomem;
+	if (!aliases) {
+		pr_err("FATAL: not enough memory to print PMU events\n");
+		return;
+	}
 	pmu = NULL;
 	j = 0;
 	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
+		bool is_cpu;
+
 		if (pmu_name && pmu->name && strcmp(pmu_name, pmu->name))
 			continue;
 
-		list_for_each_entry(alias, &pmu->aliases, list) {
-			char *name = alias->desc ? alias->name :
-				format_alias(buf, sizeof(buf), pmu, alias);
-			bool is_cpu = is_pmu_core(pmu->name) ||
-				      perf_pmu__is_hybrid(pmu->name);
+		is_cpu = is_pmu_core(pmu->name) || perf_pmu__is_hybrid(pmu->name);
 
+		list_for_each_entry(alias, &pmu->aliases, list) {
 			if (alias->deprecated && !deprecated)
 				continue;
 
 			if (event_glob != NULL &&
-			    !(strglobmatch_nocase(name, event_glob) ||
-			      (!is_cpu && strglobmatch_nocase(alias->name,
-						       event_glob)) ||
+			    !(strglobmatch_nocase(alias->name, event_glob) ||
+			      (!is_cpu &&
+			       strglobmatch_nocase(alias->name, event_glob)) ||
 			      (alias->topic &&
 			       strglobmatch_nocase(alias->topic, event_glob))))
 				continue;
 
-			if (is_cpu && !name_only && !alias->desc)
-				name = format_alias_or(buf, sizeof(buf), pmu, alias);
-
-			aliases[j].name = name;
-			if (is_cpu && !name_only && !alias->desc)
-				aliases[j].name = format_alias_or(buf,
-								  sizeof(buf),
-								  pmu, alias);
-			aliases[j].name = strdup(aliases[j].name);
-			if (!aliases[j].name)
-				goto out_enomem;
-
-			aliases[j].desc = long_desc ? alias->long_desc :
-						alias->desc;
-			aliases[j].topic = alias->topic;
-			aliases[j].str = alias->str;
-			aliases[j].pmu = pmu->name;
-			aliases[j].metric_expr = alias->metric_expr;
-			aliases[j].metric_name = alias->metric_name;
+			aliases[j].event = alias;
+			aliases[j].pmu = pmu;
 			aliases[j].is_cpu = is_cpu;
 			j++;
 		}
 		if (pmu->selectable &&
 		    (event_glob == NULL || strglobmatch(pmu->name, event_glob))) {
-			char *s;
-			if (asprintf(&s, "%s//", pmu->name) < 0)
-				goto out_enomem;
-			aliases[j].name = s;
+			aliases[j].event = NULL;
+			aliases[j].pmu = pmu;
+			aliases[j].is_cpu = is_cpu;
 			j++;
 		}
 	}
 	len = j;
 	qsort(aliases, len, sizeof(struct sevent), cmp_sevent);
 	for (j = 0; j < len; j++) {
+		char *name, *desc;
+
 		/* Skip duplicates */
 		if (j > 0 && pmu_alias_is_duplicate(&aliases[j], &aliases[j - 1]))
 			continue;
 
+		if (!aliases[j].event) {
+			/* A selectable event. */
+			snprintf(buf, sizeof(buf), "%s//", aliases[j].pmu->name);
+			name = buf;
+		} else if (aliases[j].event->desc) {
+			name = aliases[j].event->name;
+		} else {
+			if (!name_only && aliases[j].is_cpu) {
+				name = format_alias_or(buf, sizeof(buf), aliases[j].pmu,
+						       aliases[j].event);
+			} else {
+				name = format_alias(buf, sizeof(buf), aliases[j].pmu,
+						    aliases[j].event);
+			}
+		}
 		if (name_only) {
-			printf("%s ", aliases[j].name);
+			printf("%s ", name);
 			continue;
 		}
-		if (aliases[j].desc && !quiet_flag) {
-			if (numdesc++ == 0)
-				printf("\n");
-			if (aliases[j].topic && (!topic ||
-					strcmp(topic, aliases[j].topic))) {
-				printf("%s%s:\n", topic ? "\n" : "",
-						aliases[j].topic);
-				topic = aliases[j].topic;
-			}
-			printf("  %-50s\n", aliases[j].name);
-			printf("%*s", 8, "[");
-			wordwrap(aliases[j].desc, 8, columns, 0);
-			printf("]\n");
-			if (details_flag) {
-				printf("%*s%s/%s/ ", 8, "", aliases[j].pmu, aliases[j].str);
-				if (aliases[j].metric_name)
-					printf(" MetricName: %s", aliases[j].metric_name);
-				if (aliases[j].metric_expr)
-					printf(" MetricExpr: %s", aliases[j].metric_expr);
-				putchar('\n');
-			}
-		} else
-			printf("  %-50s [Kernel PMU event]\n", aliases[j].name);
 		printed++;
+		if (!aliases[j].event || !aliases[j].event->desc || quiet_flag) {
+			printf("  %-50s [Kernel PMU event]\n", name);
+			continue;
+		}
+		if (numdesc++ == 0)
+			printf("\n");
+		if (aliases[j].event->topic && (!topic ||
+						strcmp(topic, aliases[j].event->topic))) {
+			printf("%s%s:\n", topic ? "\n" : "", aliases[j].event->topic);
+			topic = aliases[j].event->topic;
+		}
+		printf("  %-50s\n", name);
+		printf("%*s", 8, "[");
+		desc = long_desc ? aliases[j].event->long_desc : aliases[j].event->desc;
+		wordwrap(desc, 8, columns, 0);
+		printf("]\n");
+		if (details_flag) {
+			printf("%*s%s/%s/ ", 8, "", aliases[j].pmu->name, aliases[j].event->str);
+			if (aliases[j].event->metric_name)
+				printf(" MetricName: %s", aliases[j].event->metric_name);
+			if (aliases[j].event->metric_expr)
+				printf(" MetricExpr: %s", aliases[j].event->metric_expr);
+			putchar('\n');
+		}
 	}
 	if (printed && pager_in_use())
 		printf("\n");
-out_free:
-	for (j = 0; j < len; j++)
-		zfree(&aliases[j].name);
+
 	zfree(&aliases);
 	return;
-
-out_enomem:
-	printf("FATAL: not enough memory to print PMU events\n");
-	if (aliases)
-		goto out_free;
 }
 
 bool pmu_have_event(const char *pname, const char *name)