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.
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/lib/api/Makefile | 2 +-
tools/lib/api/io_dir.h | 75 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 76 insertions(+), 1 deletion(-)
create mode 100644 tools/lib/api/io_dir.h
@@ -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
new file mode 100644
@@ -0,0 +1,75 @@
+/* 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>
+
+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