Switch memory_node__read and build_mem_topology from opendir/readdir
to io_dir__readdir, with smaller stack allocations. Reduces peak
memory consumption of perf record by 10kb.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/header.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 1c687b5789c0..54f7b7ec9cdd 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -44,6 +44,7 @@
 #include "build-id.h"
 #include "data.h"
 #include <api/fs/fs.h>
+#include <api/io_dir.h>
 #include "asm/bug.h"
 #include "tool.h"
 #include "time-utils.h"
@@ -1341,11 +1342,11 @@ static int memory_node__read(struct memory_node *n, unsigned long idx)
 {
 	unsigned int phys, size = 0;
 	char path[PATH_MAX];
-	struct dirent *ent;
-	DIR *dir;
+	struct io_dirent64 *ent;
+	struct io_dir dir;
 
 #define for_each_memory(mem, dir)					\
-	while ((ent = readdir(dir)))					\
+	while ((ent = io_dir__readdir(&dir)) != NULL)			\
 		if (strcmp(ent->d_name, ".") &&				\
 		    strcmp(ent->d_name, "..") &&			\
 		    sscanf(ent->d_name, "memory%u", &mem) == 1)
@@ -1354,9 +1355,9 @@ static int memory_node__read(struct memory_node *n, unsigned long idx)
 		  "%s/devices/system/node/node%lu",
 		  sysfs__mountpoint(), idx);
 
-	dir = opendir(path);
-	if (!dir) {
-		pr_warning("failed: can't open memory sysfs data\n");
+	io_dir__init(&dir, open(path, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
+	if (dir.dirfd < 0) {
+		pr_warning("failed: can't open memory sysfs data '%s'\n", path);
 		return -1;
 	}
 
@@ -1368,20 +1369,20 @@ static int memory_node__read(struct memory_node *n, unsigned long idx)
 
 	n->set = bitmap_zalloc(size);
 	if (!n->set) {
-		closedir(dir);
+		close(dir.dirfd);
 		return -ENOMEM;
 	}
 
 	n->node = idx;
 	n->size = size;
 
-	rewinddir(dir);
+	io_dir__rewinddir(&dir);
 
 	for_each_memory(phys, dir) {
 		__set_bit(phys, n->set);
 	}
 
-	closedir(dir);
+	close(dir.dirfd);
 	return 0;
 }
 
@@ -1404,8 +1405,8 @@ static int memory_node__sort(const void *a, const void *b)
 static int build_mem_topology(struct memory_node **nodesp, u64 *cntp)
 {
 	char path[PATH_MAX];
-	struct dirent *ent;
-	DIR *dir;
+	struct io_dirent64 *ent;
+	struct io_dir dir;
 	int ret = 0;
 	size_t cnt = 0, size = 0;
 	struct memory_node *nodes = NULL;
@@ -1413,14 +1414,14 @@ static int build_mem_topology(struct memory_node **nodesp, u64 *cntp)
 	scnprintf(path, PATH_MAX, "%s/devices/system/node/",
 		  sysfs__mountpoint());
 
-	dir = opendir(path);
-	if (!dir) {
+	io_dir__init(&dir, open(path, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
+	if (dir.dirfd < 0) {
 		pr_debug2("%s: couldn't read %s, does this arch have topology information?\n",
 			  __func__, path);
 		return -1;
 	}
 
-	while (!ret && (ent = readdir(dir))) {
+	while (!ret && (ent = io_dir__readdir(&dir))) {
 		unsigned int idx;
 		int r;
 
@@ -1447,7 +1448,7 @@ static int build_mem_topology(struct memory_node **nodesp, u64 *cntp)
 		ret = memory_node__read(&nodes[cnt++], idx);
 	}
 out:
-	closedir(dir);
+	close(dir.dirfd);
 	if (!ret) {
 		*cntp = cnt;
 		*nodesp = nodes;
-- 
2.43.0.rc1.413.gea7ed67945-goog

On Mon, Nov 27, 2023 at 2:09 PM Ian Rogers <irogers@google.com> wrote:
>
> Switch memory_node__read and build_mem_topology from opendir/readdir
> to io_dir__readdir, with smaller stack allocations. Reduces peak
> memory consumption of perf record by 10kb.
>
> Signed-off-by: Ian Rogers <irogers@google.com>

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung