Commit d996c726 authored by Ian Rogers's avatar Ian Rogers Committed by Namhyung Kim
Browse files

perf hwmon_pmu: Switch event discovery to io_dir__readdir 



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

Signed-off-by: default avatarIan Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250222061015.303622-8-irogers@google.com


Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
parent bb327140

tools/perf/util/hwmon_pmu.c

+17 −25
Original line number Diff line number Diff line
@@ -11,13 +11,13 @@ 
#include <sys/types.h>

#include <assert.h>

#include <ctype.h>

#include <dirent.h>

#include <fcntl.h>

#include <stddef.h>

#include <stdlib.h>

#include <string.h>

#include <api/fs/fs.h>

#include <api/io.h>

#include <api/io_dir.h>

#include <linux/kernel.h>

#include <linux/string.h>

#include <linux/zalloc.h>
@@ -235,31 +235,22 @@ static void fix_name(char *p) 


static int hwmon_pmu__read_events(struct hwmon_pmu *pmu)

{

	DIR *dir;

	struct dirent *ent;

	int dup_fd, err = 0;

	int err = 0;

	struct hashmap_entry *cur, *tmp;

	size_t bkt;

	struct io_dirent64 *ent;

	struct io_dir dir;



	if (pmu->pmu.sysfs_aliases_loaded)

		return 0;



	/*

	 * Use a dup-ed fd as closedir will close it. Use openat so that the

	 * directory contents are refreshed.

	 */

	dup_fd = openat(pmu->hwmon_dir_fd, ".", O_DIRECTORY);

	/* Use openat so that the directory contents are refreshed. */

	io_dir__init(&dir, openat(pmu->hwmon_dir_fd, ".", O_CLOEXEC | O_DIRECTORY | O_RDONLY));



	if (dup_fd == -1)

		return -ENOMEM;

	if (dir.dirfd < 0)

		return -ENOENT;



	dir = fdopendir(dup_fd);

	if (!dir) {

		close(dup_fd);

		return -ENOMEM;

	}



	while ((ent = readdir(dir)) != NULL) {

	while ((ent = io_dir__readdir(&dir)) != NULL) {

		enum hwmon_type type;

		int number;

		enum hwmon_item item;
@@ -347,7 +338,7 @@ static int hwmon_pmu__read_events(struct hwmon_pmu *pmu) 
	pmu->pmu.sysfs_aliases_loaded = true;



err_out:

	closedir(dir);

	close(dir.dirfd);

	return err;

}
@@ -702,8 +693,8 @@ int hwmon_pmu__check_alias(struct parse_events_terms *terms, struct perf_pmu_inf 
int perf_pmus__read_hwmon_pmus(struct list_head *pmus)

{

	char *line = NULL;

	DIR *class_hwmon_dir;

	struct dirent *class_hwmon_ent;

	struct io_dirent64 *class_hwmon_ent;

	struct io_dir class_hwmon_dir;

	char buf[PATH_MAX];

	const char *sysfs = sysfs__mountpoint();
@@ -711,11 +702,12 @@ int perf_pmus__read_hwmon_pmus(struct list_head *pmus) 
		return 0;



	scnprintf(buf, sizeof(buf), "%s/class/hwmon/", sysfs);

	class_hwmon_dir = opendir(buf);

	if (!class_hwmon_dir)

	io_dir__init(&class_hwmon_dir, open(buf, O_CLOEXEC | O_DIRECTORY | O_RDONLY));



	if (class_hwmon_dir.dirfd < 0)

		return 0;



	while ((class_hwmon_ent = readdir(class_hwmon_dir)) != NULL) {

	while ((class_hwmon_ent = io_dir__readdir(&class_hwmon_dir)) != NULL) {

		size_t line_len;

		int hwmon_dir, name_fd;

		struct io io;
@@ -745,7 +737,7 @@ int perf_pmus__read_hwmon_pmus(struct list_head *pmus) 
		close(name_fd);

	}

	free(line);

	closedir(class_hwmon_dir);

	close(class_hwmon_dir.dirfd);

	return 0;

}