[PATCH v2 6/7] perf parse-events: Switch tracepoints to io_dir__readdir

[Ian Rogers]

Avoid DIR allocations when scanning sysfs by using io_dir for the
readdir implementation, that allocates about 1kb on the stack.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/lib/api/io_dir.h         |  2 --
 tools/perf/util/parse-events.c | 32 +++++++++++++++++++-------------
 2 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/tools/lib/api/io_dir.h b/tools/lib/api/io_dir.h
index c84738923c96..9f07460afacc 100644
--- a/tools/lib/api/io_dir.h
+++ b/tools/lib/api/io_dir.h
@@ -89,5 +89,3 @@ static inline bool io_dir__is_dir(const struct io_dir *iod, struct io_dirent64 *
 	}
 	return dent->d_type == DT_DIR;
 }
-
-#endif
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 6c36b98875bc..35e48fe56dfa 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -17,6 +17,7 @@
 #include "strbuf.h"
 #include "debug.h"
 #include <api/fs/tracing_path.h>
+#include <api/io_dir.h>
 #include <perf/cpumap.h>
 #include <util/parse-events-bison.h>
 #include <util/parse-events-flex.h>
@@ -554,8 +555,8 @@ static int add_tracepoint_multi_event(struct parse_events_state *parse_state,
 				      struct parse_events_terms *head_config, YYLTYPE *loc)
 {
 	char *evt_path;
-	struct dirent *evt_ent;
-	DIR *evt_dir;
+	struct io_dirent64 *evt_ent;
+	struct io_dir evt_dir;
 	int ret = 0, found = 0;
 
 	evt_path = get_events_file(sys_name);
@@ -563,14 +564,14 @@ static int add_tracepoint_multi_event(struct parse_events_state *parse_state,
 		tracepoint_error(err, errno, sys_name, evt_name, loc->first_column);
 		return -1;
 	}
-	evt_dir = opendir(evt_path);
-	if (!evt_dir) {
+	io_dir__init(&evt_dir, open(evt_path, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
+	if (evt_dir.dirfd < 0) {
 		put_events_file(evt_path);
 		tracepoint_error(err, errno, sys_name, evt_name, loc->first_column);
 		return -1;
 	}
 
-	while (!ret && (evt_ent = readdir(evt_dir))) {
+	while (!ret && (evt_ent = io_dir__readdir(&evt_dir))) {
 		if (!strcmp(evt_ent->d_name, ".")
 		    || !strcmp(evt_ent->d_name, "..")
 		    || !strcmp(evt_ent->d_name, "enable")
@@ -592,7 +593,7 @@ static int add_tracepoint_multi_event(struct parse_events_state *parse_state,
 	}
 
 	put_events_file(evt_path);
-	closedir(evt_dir);
+	close(evt_dir.dirfd);
 	return ret;
 }
 
@@ -615,17 +616,23 @@ static int add_tracepoint_multi_sys(struct parse_events_state *parse_state,
 				    struct parse_events_error *err,
 				    struct parse_events_terms *head_config, YYLTYPE *loc)
 {
-	struct dirent *events_ent;
-	DIR *events_dir;
+	struct io_dirent64 *events_ent;
+	struct io_dir events_dir;
 	int ret = 0;
+	char *events_dir_path = get_tracing_file("events");
 
-	events_dir = tracing_events__opendir();
-	if (!events_dir) {
+	if (!events_dir_path) {
+		tracepoint_error(err, errno, sys_name, evt_name, loc->first_column);
+		return -1;
+	}
+	io_dir__init(&events_dir, open(events_dir_path, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
+	put_events_file(events_dir_path);
+	if (events_dir.dirfd < 0) {
 		tracepoint_error(err, errno, sys_name, evt_name, loc->first_column);
 		return -1;
 	}
 
-	while (!ret && (events_ent = readdir(events_dir))) {
+	while (!ret && (events_ent = io_dir__readdir(&events_dir))) {
 		if (!strcmp(events_ent->d_name, ".")
 		    || !strcmp(events_ent->d_name, "..")
 		    || !strcmp(events_ent->d_name, "enable")
@@ -639,8 +646,7 @@ static int add_tracepoint_multi_sys(struct parse_events_state *parse_state,
 		ret = add_tracepoint_event(parse_state, list, events_ent->d_name,
 					   evt_name, err, head_config, loc);
 	}
-
-	closedir(events_dir);
+	close(events_dir.dirfd);
 	return ret;
 }
 
-- 
2.48.1.502.g6dc24dfdaf-goog