[PATCH v1 0/6] Add io_dir to avoid memory overhead from opendir

[PATCH v1 0/6] Add io_dir to avoid memory overhead from opendir

[Ian Rogers]

glibc's opendir allocates a minimum of 32kb, when called recursively
for a directory tree the memory consumption can add up - nearly 300kb
during perf start-up when processing modules. Add a stack allocated
variant of readdir sized a little more than 1kb

This was previously part of the memory saving change set:
https://lore.kernel.org/lkml/20231127220902.1315692-1-irogers@google.com/
It is separated here and a feature check and syscall workaround for
missing getdents64 added.

Ian Rogers (6):
  tools build: Add a feature test for getdents64
  tools lib api: Add io_dir an allocation free readdir alternative
  perf maps: Switch modules tree walk to io_dir__readdir
  perf pmu: Switch to io_dir__readdir
  perf header: Switch mem topology to io_dir__readdir
  perf events: Remove scandir in thread synthesis

 tools/build/Makefile.feature          |  1 +
 tools/build/feature/Makefile          |  4 ++
 tools/build/feature/test-all.c        |  5 ++
 tools/build/feature/test-getdents64.c | 12 ++++
 tools/lib/api/Makefile                |  2 +-
 tools/lib/api/io_dir.h                | 84 +++++++++++++++++++++++++++
 tools/perf/Makefile.config            |  4 ++
 tools/perf/util/header.c              | 31 +++++-----
 tools/perf/util/machine.c             | 19 +++---
 tools/perf/util/pmu.c                 | 48 ++++++---------
 tools/perf/util/pmus.c                | 30 ++++------
 tools/perf/util/synthetic-events.c    | 22 +++----
 12 files changed, 177 insertions(+), 85 deletions(-)
 create mode 100644 tools/build/feature/test-getdents64.c
 create mode 100644 tools/lib/api/io_dir.h

-- 
2.43.0.rc2.451.g8631bc7472-goog

[PATCH v1 1/6] tools build: Add a feature test for getdents64

[Ian Rogers]

getdents64 may be missing from certain libcs, add a feature test to
determine when such a libc is being used.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/build/Makefile.feature          |  1 +
 tools/build/feature/Makefile          |  4 ++++
 tools/build/feature/test-all.c        |  5 +++++
 tools/build/feature/test-getdents64.c | 12 ++++++++++++
 4 files changed, 22 insertions(+)
 create mode 100644 tools/build/feature/test-getdents64.c

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 64df118376df..f051d4d8c71c 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -58,6 +58,7 @@ FEATURE_TESTS_BASIC :=                  \
         pthread-attr-setaffinity-np     \
         pthread-barrier     		\
         reallocarray                    \
+        getdents64                      \
         stackprotector-all              \
         timerfd                         \
         libdw-dwarf-unwind              \
diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 37722e509eb9..5efe89c3b0a6 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -21,6 +21,7 @@ FILES=                                          \
          test-disassembler-four-args.bin        \
          test-disassembler-init-styled.bin	\
          test-reallocarray.bin			\
+         test-getdents64.bin			\
          test-libbfd-liberty.bin                \
          test-libbfd-liberty-z.bin              \
          test-cplus-demangle.bin                \
@@ -262,6 +263,9 @@ $(OUTPUT)test-disassembler-init-styled.bin:
 $(OUTPUT)test-reallocarray.bin:
 	$(BUILD)
 
+$(OUTPUT)test-getdents64.bin:
+	$(BUILD)
+
 $(OUTPUT)test-libbfd-liberty.bin:
 	$(CC) $(CFLAGS) -Wall -Werror -o $@ test-libbfd.c -DPACKAGE='"perf"' $(LDFLAGS) -lbfd -ldl -liberty
 
diff --git a/tools/build/feature/test-all.c b/tools/build/feature/test-all.c
index 6f4bf386a3b5..c65096f75032 100644
--- a/tools/build/feature/test-all.c
+++ b/tools/build/feature/test-all.c
@@ -166,6 +166,10 @@
 # include "test-reallocarray.c"
 #undef main
 
+#define main main_test_getdents64
+# include "test-getdents64.c"
+#undef main
+
 #define main main_test_disassembler_four_args
 # include "test-disassembler-four-args.c"
 #undef main
@@ -216,6 +220,7 @@ int main(int argc, char *argv[])
 	main_test_setns();
 	main_test_libaio();
 	main_test_reallocarray();
+	main_test_getdents64();
 	main_test_disassembler_four_args();
 	main_test_libzstd();
 
diff --git a/tools/build/feature/test-getdents64.c b/tools/build/feature/test-getdents64.c
new file mode 100644
index 000000000000..f7c9df1e2f05
--- /dev/null
+++ b/tools/build/feature/test-getdents64.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stddef.h>
+#define _GNU_SOURCE
+#include <dirent.h>
+
+int main(void)
+{
+	char buf[128];
+	return (int)getdents64(0, buf, sizeof(buf));
+}
+
+#undef _GNU_SOURCE
-- 
2.43.0.rc2.451.g8631bc7472-goog

[PATCH v1 2/6] tools lib api: Add io_dir an allocation free readdir alternative

[Ian Rogers]

glibc's opendir allocates a minimum of 32kb, when called recursively
for a directory tree the memory consumption can add up - nearly 300kb
during perf start-up when processing modules. Add a stack allocated
variant of readdir sized a little more than 1kb.

As getdents64 may be missing from libc, add support using syscall.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/lib/api/Makefile     |  2 +-
 tools/lib/api/io_dir.h     | 84 ++++++++++++++++++++++++++++++++++++++
 tools/perf/Makefile.config |  4 ++
 3 files changed, 89 insertions(+), 1 deletion(-)
 create mode 100644 tools/lib/api/io_dir.h

diff --git a/tools/lib/api/Makefile b/tools/lib/api/Makefile
index 044860ac1ed1..186aa407de8c 100644
--- a/tools/lib/api/Makefile
+++ b/tools/lib/api/Makefile
@@ -99,7 +99,7 @@ install_lib: $(LIBFILE)
 		$(call do_install_mkdir,$(libdir_SQ)); \
 		cp -fpR $(LIBFILE) $(DESTDIR)$(libdir_SQ)
 
-HDRS := cpu.h debug.h io.h
+HDRS := cpu.h debug.h io.h io_dir.h
 FD_HDRS := fd/array.h
 FS_HDRS := fs/fs.h fs/tracing_path.h
 INSTALL_HDRS_PFX := $(DESTDIR)$(prefix)/include/api
diff --git a/tools/lib/api/io_dir.h b/tools/lib/api/io_dir.h
new file mode 100644
index 000000000000..9b702497e05c
--- /dev/null
+++ b/tools/lib/api/io_dir.h
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+/*
+ * Lightweight directory reading library.
+ */
+#ifndef __API_IO_DIR__
+#define __API_IO_DIR__
+
+#include <dirent.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+#ifndef HAVE_GETDENTS64
+#include <sys/syscall.h>
+
+static inline ssize_t getdents64(int fd, void *dirp, size_t count)
+{
+	return syscall(SYS_getdents64, fd, dirp, count);
+}
+#endif
+
+struct io_dirent64 {
+	ino64_t        d_ino;    /* 64-bit inode number */
+	off64_t        d_off;    /* 64-bit offset to next structure */
+	unsigned short d_reclen; /* Size of this dirent */
+	unsigned char  d_type;   /* File type */
+	char           d_name[NAME_MAX + 1]; /* Filename (null-terminated) */
+};
+
+struct io_dir {
+	int dirfd;
+	ssize_t available_bytes;
+	struct io_dirent64 *next;
+	struct io_dirent64 buff[4];
+};
+
+static inline void io_dir__init(struct io_dir *iod, int dirfd)
+{
+	iod->dirfd = dirfd;
+	iod->available_bytes = 0;
+}
+
+static inline void io_dir__rewinddir(struct io_dir *iod)
+{
+	lseek(iod->dirfd, 0, SEEK_SET);
+	iod->available_bytes = 0;
+}
+
+static inline struct io_dirent64 *io_dir__readdir(struct io_dir *iod)
+{
+	struct io_dirent64 *entry;
+
+	if (iod->available_bytes <= 0) {
+		ssize_t rc = getdents64(iod->dirfd, iod->buff, sizeof(iod->buff));
+
+		if (rc <= 0)
+			return NULL;
+		iod->available_bytes = rc;
+		iod->next = iod->buff;
+	}
+	entry = iod->next;
+	iod->next = (struct io_dirent64 *)((char *)entry + entry->d_reclen);
+	iod->available_bytes -= entry->d_reclen;
+	return entry;
+}
+
+static inline bool io_dir__is_dir(const struct io_dir *iod, struct io_dirent64 *dent)
+{
+	if (dent->d_type == DT_UNKNOWN) {
+		struct stat st;
+
+		if (fstatat(iod->dirfd, dent->d_name, &st, /*flags=*/0))
+			return false;
+
+		if (S_ISDIR(st.st_mode)) {
+			dent->d_type = DT_DIR;
+			return true;
+		}
+	}
+	return dent->d_type == DT_DIR;
+}
+
+#endif
diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index aa55850fbc21..1cef1ab4ddb7 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -357,6 +357,10 @@ ifeq ($(feature-stackprotector-all), 1)
   CORE_CFLAGS += -fstack-protector-all
 endif
 
+ifeq ($(feature-getdents64), 1)
+  CFLAGS += -DHAVE_GETDENTS64
+endif
+
 ifeq ($(DEBUG),0)
   ifeq ($(feature-fortify-source), 1)
     CORE_CFLAGS += -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2
-- 
2.43.0.rc2.451.g8631bc7472-goog

[PATCH v1 3/6] perf maps: Switch modules tree walk to io_dir__readdir

[Ian Rogers]

Compared to glibc's opendir/readdir this lowers the max RSS of perf
record by 1.8MB on a Debian machine.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/machine.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index c5de5363b5e7..b6831a1f909d 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -36,6 +36,7 @@
 #include <internal/lib.h> // page_size
 #include "cgroup.h"
 #include "arm64-frame-pointer-unwind-support.h"
+#include <api/io_dir.h>
 
 #include <linux/ctype.h>
 #include <symbol/kallsyms.h>
@@ -1551,25 +1552,21 @@ static int maps__set_module_path(struct maps *maps, const char *path, struct kmo
 
 static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, int depth)
 {
-	struct dirent *dent;
-	DIR *dir = opendir(dir_name);
+	struct io_dirent64 *dent;
+	struct io_dir iod;
 	int ret = 0;
 
-	if (!dir) {
+	io_dir__init(&iod, open(dir_name, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
+	if (iod.dirfd < 0) {
 		pr_debug("%s: cannot open %s dir\n", __func__, dir_name);
 		return -1;
 	}
 
-	while ((dent = readdir(dir)) != NULL) {
+	while ((dent = io_dir__readdir(&iod)) != NULL) {
 		char path[PATH_MAX];
-		struct stat st;
 
-		/*sshfs might return bad dent->d_type, so we have to stat*/
 		path__join(path, sizeof(path), dir_name, dent->d_name);
-		if (stat(path, &st))
-			continue;
-
-		if (S_ISDIR(st.st_mode)) {
+		if (io_dir__is_dir(&iod, dent)) {
 			if (!strcmp(dent->d_name, ".") ||
 			    !strcmp(dent->d_name, ".."))
 				continue;
@@ -1602,7 +1599,7 @@ static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, i
 	}
 
 out:
-	closedir(dir);
+	close(iod.dirfd);
 	return ret;
 }
 
-- 
2.43.0.rc2.451.g8631bc7472-goog

[PATCH v1 4/6] perf pmu: Switch 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@google.com>
---
 tools/perf/util/pmu.c  | 48 +++++++++++++++++-------------------------
 tools/perf/util/pmus.c | 30 ++++++++++----------------
 2 files changed, 30 insertions(+), 48 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 3c9609944a2f..cddb82123a1e 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -12,6 +12,7 @@
 #include <stdbool.h>
 #include <dirent.h>
 #include <api/fs/fs.h>
+#include <api/io_dir.h>
 #include <locale.h>
 #include <fnmatch.h>
 #include <math.h>
@@ -184,19 +185,17 @@ static void perf_pmu_format__load(const struct perf_pmu *pmu, struct perf_pmu_fo
  */
 int perf_pmu__format_parse(struct perf_pmu *pmu, int dirfd, bool eager_load)
 {
-	struct dirent *evt_ent;
-	DIR *format_dir;
+	struct io_dirent64 *evt_ent;
+	struct io_dir format_dir;
 	int ret = 0;
 
-	format_dir = fdopendir(dirfd);
-	if (!format_dir)
-		return -EINVAL;
+	io_dir__init(&format_dir, dirfd);
 
-	while ((evt_ent = readdir(format_dir)) != NULL) {
+	while ((evt_ent = io_dir__readdir(&format_dir)) != NULL) {
 		struct perf_pmu_format *format;
 		char *name = evt_ent->d_name;
 
-		if (!strcmp(name, ".") || !strcmp(name, ".."))
+		if (io_dir__is_dir(&format_dir, evt_ent))
 			continue;
 
 		format = perf_pmu__new_format(&pmu->format, name);
@@ -223,7 +222,7 @@ int perf_pmu__format_parse(struct perf_pmu *pmu, int dirfd, bool eager_load)
 		}
 	}
 
-	closedir(format_dir);
+	close(format_dir.dirfd);
 	return ret;
 }
 
@@ -599,8 +598,8 @@ static inline bool pmu_alias_info_file(const char *name)
 static int pmu_aliases_parse(struct perf_pmu *pmu)
 {
 	char path[PATH_MAX];
-	struct dirent *evt_ent;
-	DIR *event_dir;
+	struct io_dirent64 *evt_ent;
+	struct io_dir event_dir;
 	size_t len;
 	int fd, dir_fd;
 
@@ -615,13 +614,9 @@ static int pmu_aliases_parse(struct perf_pmu *pmu)
 		return 0;
 	}
 
-	event_dir = fdopendir(dir_fd);
-	if (!event_dir){
-		close (dir_fd);
-		return -EINVAL;
-	}
+	io_dir__init(&event_dir, dir_fd);
 
-	while ((evt_ent = readdir(event_dir))) {
+	while ((evt_ent = io_dir__readdir(&event_dir))) {
 		char *name = evt_ent->d_name;
 		FILE *file;
 
@@ -651,7 +646,6 @@ static int pmu_aliases_parse(struct perf_pmu *pmu)
 		fclose(file);
 	}
 
-	closedir(event_dir);
 	close (dir_fd);
 	pmu->sysfs_aliases_loaded = true;
 	return 0;
@@ -1883,10 +1877,9 @@ static void perf_pmu__del_caps(struct perf_pmu *pmu)
  */
 int perf_pmu__caps_parse(struct perf_pmu *pmu)
 {
-	struct stat st;
 	char caps_path[PATH_MAX];
-	DIR *caps_dir;
-	struct dirent *evt_ent;
+	struct io_dir caps_dir;
+	struct io_dirent64 *evt_ent;
 	int caps_fd;
 
 	if (pmu->caps_initialized)
@@ -1897,24 +1890,21 @@ int perf_pmu__caps_parse(struct perf_pmu *pmu)
 	if (!perf_pmu__pathname_scnprintf(caps_path, sizeof(caps_path), pmu->name, "caps"))
 		return -1;
 
-	if (stat(caps_path, &st) < 0) {
+	caps_fd = open(caps_path, O_CLOEXEC | O_DIRECTORY | O_RDONLY);
+	if (caps_fd == -1) {
 		pmu->caps_initialized = true;
 		return 0;	/* no error if caps does not exist */
 	}
 
-	caps_dir = opendir(caps_path);
-	if (!caps_dir)
-		return -EINVAL;
-
-	caps_fd = dirfd(caps_dir);
+	io_dir__init(&caps_dir, caps_fd);
 
-	while ((evt_ent = readdir(caps_dir)) != NULL) {
+	while ((evt_ent = io_dir__readdir(&caps_dir)) != NULL) {
 		char *name = evt_ent->d_name;
 		char value[128];
 		FILE *file;
 		int fd;
 
-		if (!strcmp(name, ".") || !strcmp(name, ".."))
+		if (io_dir__is_dir(&caps_dir, evt_ent))
 			continue;
 
 		fd = openat(caps_fd, name, O_RDONLY);
@@ -1936,7 +1926,7 @@ int perf_pmu__caps_parse(struct perf_pmu *pmu)
 		fclose(file);
 	}
 
-	closedir(caps_dir);
+	close(caps_fd);
 
 	pmu->caps_initialized = true;
 	return pmu->nr_caps;
diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
index ce4931461741..65b23b98666b 100644
--- a/tools/perf/util/pmus.c
+++ b/tools/perf/util/pmus.c
@@ -3,10 +3,10 @@
 #include <linux/list_sort.h>
 #include <linux/string.h>
 #include <linux/zalloc.h>
+#include <api/io_dir.h>
 #include <subcmd/pager.h>
 #include <sys/types.h>
 #include <ctype.h>
-#include <dirent.h>
 #include <pthread.h>
 #include <string.h>
 #include <unistd.h>
@@ -184,8 +184,8 @@ static int pmus_cmp(void *priv __maybe_unused,
 static void pmu_read_sysfs(bool core_only)
 {
 	int fd;
-	DIR *dir;
-	struct dirent *dent;
+	struct io_dir dir;
+	struct io_dirent64 *dent;
 
 	if (read_sysfs_all_pmus || (core_only && read_sysfs_core_pmus))
 		return;
@@ -194,13 +194,9 @@ static void pmu_read_sysfs(bool core_only)
 	if (fd < 0)
 		return;
 
-	dir = fdopendir(fd);
-	if (!dir) {
-		close(fd);
-		return;
-	}
+	io_dir__init(&dir, fd);
 
-	while ((dent = readdir(dir))) {
+	while ((dent = io_dir__readdir(&dir)) != NULL) {
 		if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
 			continue;
 		if (core_only && !is_pmu_core(dent->d_name))
@@ -209,7 +205,7 @@ static void pmu_read_sysfs(bool core_only)
 		perf_pmu__find2(fd, dent->d_name);
 	}
 
-	closedir(dir);
+	close(fd);
 	if (list_empty(&core_pmus)) {
 		if (!perf_pmu__create_placeholder_core_pmu(&core_pmus))
 			pr_err("Failure to set up any core PMUs\n");
@@ -563,8 +559,8 @@ bool perf_pmus__supports_extended_type(void)
 char *perf_pmus__default_pmu_name(void)
 {
 	int fd;
-	DIR *dir;
-	struct dirent *dent;
+	struct io_dir dir;
+	struct io_dirent64 *dent;
 	char *result = NULL;
 
 	if (!list_empty(&core_pmus))
@@ -574,13 +570,9 @@ char *perf_pmus__default_pmu_name(void)
 	if (fd < 0)
 		return strdup("cpu");
 
-	dir = fdopendir(fd);
-	if (!dir) {
-		close(fd);
-		return strdup("cpu");
-	}
+	io_dir__init(&dir, fd);
 
-	while ((dent = readdir(dir))) {
+	while ((dent = io_dir__readdir(&dir)) != NULL) {
 		if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
 			continue;
 		if (is_pmu_core(dent->d_name)) {
@@ -589,7 +581,7 @@ char *perf_pmus__default_pmu_name(void)
 		}
 	}
 
-	closedir(dir);
+	close(fd);
 	return result ?: strdup("cpu");
 }
 
-- 
2.43.0.rc2.451.g8631bc7472-goog

[PATCH v1 5/6] perf header: Switch mem topology to io_dir__readdir

[Ian Rogers]

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 08cc2febabde..d4a3e28376fd 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;
 
@@ -1449,7 +1450,7 @@ static int build_mem_topology(struct memory_node **nodesp, u64 *cntp)
 			cnt += 1;
 	}
 out:
-	closedir(dir);
+	close(dir.dirfd);
 	if (!ret) {
 		*cntp = cnt;
 		*nodesp = nodes;
-- 
2.43.0.rc2.451.g8631bc7472-goog

[PATCH v1 6/6] perf events: Remove scandir in thread synthesis

[Ian Rogers]

This avoids scanddir reading the directory into memory that's
allocated and instead allocates on the stack.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/synthetic-events.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index a0579c7d7b9e..7cc38f2a0e9e 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -38,6 +38,7 @@
 #include <uapi/linux/mman.h> /* To get things like MAP_HUGETLB even on older libc headers */
 #include <api/fs/fs.h>
 #include <api/io.h>
+#include <api/io_dir.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -751,10 +752,10 @@ static int __event__synthesize_thread(union perf_event *comm_event,
 				      bool needs_mmap, bool mmap_data)
 {
 	char filename[PATH_MAX];
-	struct dirent **dirent;
+	struct io_dir iod;
+	struct io_dirent64 *dent;
 	pid_t tgid, ppid;
 	int rc = 0;
-	int i, n;
 
 	/* special case: only send one comm event using passed in pid */
 	if (!full) {
@@ -786,16 +787,19 @@ static int __event__synthesize_thread(union perf_event *comm_event,
 	snprintf(filename, sizeof(filename), "%s/proc/%d/task",
 		 machine->root_dir, pid);
 
-	n = scandir(filename, &dirent, filter_task, NULL);
-	if (n < 0)
-		return n;
+	io_dir__init(&iod, open(filename, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
+	if (iod.dirfd < 0)
+		return -1;
 
-	for (i = 0; i < n; i++) {
+	while ((dent = io_dir__readdir(&iod)) != NULL) {
 		char *end;
 		pid_t _pid;
 		bool kernel_thread = false;
 
-		_pid = strtol(dirent[i]->d_name, &end, 10);
+		if (!isdigit(dent->d_name[0]))
+			continue;
+
+		_pid = strtol(dent->d_name, &end, 10);
 		if (*end)
 			continue;
 
@@ -829,9 +833,7 @@ static int __event__synthesize_thread(union perf_event *comm_event,
 		}
 	}
 
-	for (i = 0; i < n; i++)
-		zfree(&dirent[i]);
-	free(dirent);
+	close(iod.dirfd);
 
 	return rc;
 }
-- 
2.43.0.rc2.451.g8631bc7472-goog

Re: [PATCH v1 2/6] tools lib api: Add io_dir an allocation free readdir alternative

[Namhyung Kim]

On Wed, Dec 6, 2023 at 9:04 PM Ian Rogers <irogers@google.com> wrote:
>
> glibc's opendir allocates a minimum of 32kb, when called recursively
> for a directory tree the memory consumption can add up - nearly 300kb
> during perf start-up when processing modules. Add a stack allocated
> variant of readdir sized a little more than 1kb.
>
> As getdents64 may be missing from libc, add support using syscall.

Unfortunately my alpine build has:

In file included from util/machine.c:2:
/build/libapi/include/api/io_dir.h:17:23: error: conflicting types for
'getdents'; have 'ssize_t(int,  void *, size_t)' {aka 'long int(int,
void *, long unsigned int)'}
   17 | static inline ssize_t getdents64(int fd, void *dirp, size_t count)
      |                       ^~~~~~~~~~
/usr/include/dirent.h:52:5: note: previous declaration of 'getdents'
with type 'int(int,  struct dirent *, size_t)' {aka 'int(int,  struct
dirent *, long unsigned int)'}
   52 | int getdents(int, struct dirent *, size_t);
      |     ^~~~~~~~

Thanks,
Namhyung

>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/lib/api/Makefile     |  2 +-
>  tools/lib/api/io_dir.h     | 84 ++++++++++++++++++++++++++++++++++++++
>  tools/perf/Makefile.config |  4 ++
>  3 files changed, 89 insertions(+), 1 deletion(-)
>  create mode 100644 tools/lib/api/io_dir.h
>
> diff --git a/tools/lib/api/Makefile b/tools/lib/api/Makefile
> index 044860ac1ed1..186aa407de8c 100644
> --- a/tools/lib/api/Makefile
> +++ b/tools/lib/api/Makefile
> @@ -99,7 +99,7 @@ install_lib: $(LIBFILE)
>                 $(call do_install_mkdir,$(libdir_SQ)); \
>                 cp -fpR $(LIBFILE) $(DESTDIR)$(libdir_SQ)
>
> -HDRS := cpu.h debug.h io.h
> +HDRS := cpu.h debug.h io.h io_dir.h
>  FD_HDRS := fd/array.h
>  FS_HDRS := fs/fs.h fs/tracing_path.h
>  INSTALL_HDRS_PFX := $(DESTDIR)$(prefix)/include/api
> diff --git a/tools/lib/api/io_dir.h b/tools/lib/api/io_dir.h
> new file mode 100644
> index 000000000000..9b702497e05c
> --- /dev/null
> +++ b/tools/lib/api/io_dir.h
> @@ -0,0 +1,84 @@
> +/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
> +/*
> + * Lightweight directory reading library.
> + */
> +#ifndef __API_IO_DIR__
> +#define __API_IO_DIR__
> +
> +#include <dirent.h>
> +#include <fcntl.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <sys/stat.h>
> +
> +#ifndef HAVE_GETDENTS64
> +#include <sys/syscall.h>
> +
> +static inline ssize_t getdents64(int fd, void *dirp, size_t count)
> +{
> +       return syscall(SYS_getdents64, fd, dirp, count);
> +}
> +#endif
> +
> +struct io_dirent64 {
> +       ino64_t        d_ino;    /* 64-bit inode number */
> +       off64_t        d_off;    /* 64-bit offset to next structure */
> +       unsigned short d_reclen; /* Size of this dirent */
> +       unsigned char  d_type;   /* File type */
> +       char           d_name[NAME_MAX + 1]; /* Filename (null-terminated) */
> +};
> +
> +struct io_dir {
> +       int dirfd;
> +       ssize_t available_bytes;
> +       struct io_dirent64 *next;
> +       struct io_dirent64 buff[4];
> +};
> +
> +static inline void io_dir__init(struct io_dir *iod, int dirfd)
> +{
> +       iod->dirfd = dirfd;
> +       iod->available_bytes = 0;
> +}
> +
> +static inline void io_dir__rewinddir(struct io_dir *iod)
> +{
> +       lseek(iod->dirfd, 0, SEEK_SET);
> +       iod->available_bytes = 0;
> +}
> +
> +static inline struct io_dirent64 *io_dir__readdir(struct io_dir *iod)
> +{
> +       struct io_dirent64 *entry;
> +
> +       if (iod->available_bytes <= 0) {
> +               ssize_t rc = getdents64(iod->dirfd, iod->buff, sizeof(iod->buff));
> +
> +               if (rc <= 0)
> +                       return NULL;
> +               iod->available_bytes = rc;
> +               iod->next = iod->buff;
> +       }
> +       entry = iod->next;
> +       iod->next = (struct io_dirent64 *)((char *)entry + entry->d_reclen);
> +       iod->available_bytes -= entry->d_reclen;
> +       return entry;
> +}
> +
> +static inline bool io_dir__is_dir(const struct io_dir *iod, struct io_dirent64 *dent)
> +{
> +       if (dent->d_type == DT_UNKNOWN) {
> +               struct stat st;
> +
> +               if (fstatat(iod->dirfd, dent->d_name, &st, /*flags=*/0))
> +                       return false;
> +
> +               if (S_ISDIR(st.st_mode)) {
> +                       dent->d_type = DT_DIR;
> +                       return true;
> +               }
> +       }
> +       return dent->d_type == DT_DIR;
> +}
> +
> +#endif
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index aa55850fbc21..1cef1ab4ddb7 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -357,6 +357,10 @@ ifeq ($(feature-stackprotector-all), 1)
>    CORE_CFLAGS += -fstack-protector-all
>  endif
>
> +ifeq ($(feature-getdents64), 1)
> +  CFLAGS += -DHAVE_GETDENTS64
> +endif
> +
>  ifeq ($(DEBUG),0)
>    ifeq ($(feature-fortify-source), 1)
>      CORE_CFLAGS += -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2
> --
> 2.43.0.rc2.451.g8631bc7472-goog
>

Re: [PATCH v1 2/6] tools lib api: Add io_dir an allocation free readdir alternative

[Ian Rogers]

On Mon, Dec 11, 2023 at 3:25 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> On Wed, Dec 6, 2023 at 9:04 PM Ian Rogers <irogers@google.com> wrote:
> >
> > glibc's opendir allocates a minimum of 32kb, when called recursively
> > for a directory tree the memory consumption can add up - nearly 300kb
> > during perf start-up when processing modules. Add a stack allocated
> > variant of readdir sized a little more than 1kb.
> >
> > As getdents64 may be missing from libc, add support using syscall.
>
> Unfortunately my alpine build has:
>
> In file included from util/machine.c:2:
> /build/libapi/include/api/io_dir.h:17:23: error: conflicting types for
> 'getdents'; have 'ssize_t(int,  void *, size_t)' {aka 'long int(int,
> void *, long unsigned int)'}
>    17 | static inline ssize_t getdents64(int fd, void *dirp, size_t count)
>       |                       ^~~~~~~~~~
> /usr/include/dirent.h:52:5: note: previous declaration of 'getdents'
> with type 'int(int,  struct dirent *, size_t)' {aka 'int(int,  struct
> dirent *, long unsigned int)'}
>    52 | int getdents(int, struct dirent *, size_t);
>       |     ^~~~~~~~

Presumably there is a #define getdents64 getdents .. Could we stop
caring about this version of Alpine linux?

Thanks,
Ian

> Thanks,
> Namhyung
>
> >
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > ---
> >  tools/lib/api/Makefile     |  2 +-
> >  tools/lib/api/io_dir.h     | 84 ++++++++++++++++++++++++++++++++++++++
> >  tools/perf/Makefile.config |  4 ++
> >  3 files changed, 89 insertions(+), 1 deletion(-)
> >  create mode 100644 tools/lib/api/io_dir.h
> >
> > diff --git a/tools/lib/api/Makefile b/tools/lib/api/Makefile
> > index 044860ac1ed1..186aa407de8c 100644
> > --- a/tools/lib/api/Makefile
> > +++ b/tools/lib/api/Makefile
> > @@ -99,7 +99,7 @@ install_lib: $(LIBFILE)
> >                 $(call do_install_mkdir,$(libdir_SQ)); \
> >                 cp -fpR $(LIBFILE) $(DESTDIR)$(libdir_SQ)
> >
> > -HDRS := cpu.h debug.h io.h
> > +HDRS := cpu.h debug.h io.h io_dir.h
> >  FD_HDRS := fd/array.h
> >  FS_HDRS := fs/fs.h fs/tracing_path.h
> >  INSTALL_HDRS_PFX := $(DESTDIR)$(prefix)/include/api
> > diff --git a/tools/lib/api/io_dir.h b/tools/lib/api/io_dir.h
> > new file mode 100644
> > index 000000000000..9b702497e05c
> > --- /dev/null
> > +++ b/tools/lib/api/io_dir.h
> > @@ -0,0 +1,84 @@
> > +/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
> > +/*
> > + * Lightweight directory reading library.
> > + */
> > +#ifndef __API_IO_DIR__
> > +#define __API_IO_DIR__
> > +
> > +#include <dirent.h>
> > +#include <fcntl.h>
> > +#include <stdlib.h>
> > +#include <unistd.h>
> > +#include <sys/stat.h>
> > +
> > +#ifndef HAVE_GETDENTS64
> > +#include <sys/syscall.h>
> > +
> > +static inline ssize_t getdents64(int fd, void *dirp, size_t count)
> > +{
> > +       return syscall(SYS_getdents64, fd, dirp, count);
> > +}
> > +#endif
> > +
> > +struct io_dirent64 {
> > +       ino64_t        d_ino;    /* 64-bit inode number */
> > +       off64_t        d_off;    /* 64-bit offset to next structure */
> > +       unsigned short d_reclen; /* Size of this dirent */
> > +       unsigned char  d_type;   /* File type */
> > +       char           d_name[NAME_MAX + 1]; /* Filename (null-terminated) */
> > +};
> > +
> > +struct io_dir {
> > +       int dirfd;
> > +       ssize_t available_bytes;
> > +       struct io_dirent64 *next;
> > +       struct io_dirent64 buff[4];
> > +};
> > +
> > +static inline void io_dir__init(struct io_dir *iod, int dirfd)
> > +{
> > +       iod->dirfd = dirfd;
> > +       iod->available_bytes = 0;
> > +}
> > +
> > +static inline void io_dir__rewinddir(struct io_dir *iod)
> > +{
> > +       lseek(iod->dirfd, 0, SEEK_SET);
> > +       iod->available_bytes = 0;
> > +}
> > +
> > +static inline struct io_dirent64 *io_dir__readdir(struct io_dir *iod)
> > +{
> > +       struct io_dirent64 *entry;
> > +
> > +       if (iod->available_bytes <= 0) {
> > +               ssize_t rc = getdents64(iod->dirfd, iod->buff, sizeof(iod->buff));
> > +
> > +               if (rc <= 0)
> > +                       return NULL;
> > +               iod->available_bytes = rc;
> > +               iod->next = iod->buff;
> > +       }
> > +       entry = iod->next;
> > +       iod->next = (struct io_dirent64 *)((char *)entry + entry->d_reclen);
> > +       iod->available_bytes -= entry->d_reclen;
> > +       return entry;
> > +}
> > +
> > +static inline bool io_dir__is_dir(const struct io_dir *iod, struct io_dirent64 *dent)
> > +{
> > +       if (dent->d_type == DT_UNKNOWN) {
> > +               struct stat st;
> > +
> > +               if (fstatat(iod->dirfd, dent->d_name, &st, /*flags=*/0))
> > +                       return false;
> > +
> > +               if (S_ISDIR(st.st_mode)) {
> > +                       dent->d_type = DT_DIR;
> > +                       return true;
> > +               }
> > +       }
> > +       return dent->d_type == DT_DIR;
> > +}
> > +
> > +#endif
> > diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> > index aa55850fbc21..1cef1ab4ddb7 100644
> > --- a/tools/perf/Makefile.config
> > +++ b/tools/perf/Makefile.config
> > @@ -357,6 +357,10 @@ ifeq ($(feature-stackprotector-all), 1)
> >    CORE_CFLAGS += -fstack-protector-all
> >  endif
> >
> > +ifeq ($(feature-getdents64), 1)
> > +  CFLAGS += -DHAVE_GETDENTS64
> > +endif
> > +
> >  ifeq ($(DEBUG),0)
> >    ifeq ($(feature-fortify-source), 1)
> >      CORE_CFLAGS += -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2
> > --
> > 2.43.0.rc2.451.g8631bc7472-goog
> >

Re: [PATCH v1 2/6] tools lib api: Add io_dir an allocation free readdir alternative

[Namhyung Kim]

On Mon, Dec 11, 2023 at 3:54 PM Ian Rogers <irogers@google.com> wrote:
>
> On Mon, Dec 11, 2023 at 3:25 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > On Wed, Dec 6, 2023 at 9:04 PM Ian Rogers <irogers@google.com> wrote:
> > >
> > > glibc's opendir allocates a minimum of 32kb, when called recursively
> > > for a directory tree the memory consumption can add up - nearly 300kb
> > > during perf start-up when processing modules. Add a stack allocated
> > > variant of readdir sized a little more than 1kb.
> > >
> > > As getdents64 may be missing from libc, add support using syscall.
> >
> > Unfortunately my alpine build has:
> >
> > In file included from util/machine.c:2:
> > /build/libapi/include/api/io_dir.h:17:23: error: conflicting types for
> > 'getdents'; have 'ssize_t(int,  void *, size_t)' {aka 'long int(int,
> > void *, long unsigned int)'}
> >    17 | static inline ssize_t getdents64(int fd, void *dirp, size_t count)
> >       |                       ^~~~~~~~~~
> > /usr/include/dirent.h:52:5: note: previous declaration of 'getdents'
> > with type 'int(int,  struct dirent *, size_t)' {aka 'int(int,  struct
> > dirent *, long unsigned int)'}
> >    52 | int getdents(int, struct dirent *, size_t);
> >       |     ^~~~~~~~
>
> Presumably there is a #define getdents64 getdents .. Could we stop
> caring about this version of Alpine linux?

Right, there's a #define:

https://git.musl-libc.org/cgit/musl/tree/include/dirent.h#n68

But I'm not sure ignoring Alpine linux is a good idea.
Maybe we can add a #undef right before?

Thanks,
Namhyung