optimize readdir() open calls to be dealt with directly via 'fd' (#18762)

cmd/os-instrumented.go

@@ -39,6 +39,8 @@ const (
 	osMetricRename
 	osMetricOpenFileW
 	osMetricOpenFileR
+	osMetricOpenFileWFd
+	osMetricOpenFileRFd
 	osMetricOpen
 	osMetricOpenFileDirectIO
 	osMetricLstat

cmd/os_unix.go

@@ -39,6 +39,22 @@ func access(name string) error {
 	return nil
 }
 
+// openFileWithFD return 'fd' based file descriptor
+func openFileWithFD(name string, flag int, perm os.FileMode) (fd int, err error) {
+	switch flag & writeMode {
+	case writeMode:
+		defer updateOSMetrics(osMetricOpenFileWFd, name)(err)
+	default:
+		defer updateOSMetrics(osMetricOpenFileRFd, name)(err)
+	}
+	var e error
+	fd, e = syscall.Open(name, flag|syscall.O_CLOEXEC, uint32(perm))
+	if e != nil {
+		return -1, &os.PathError{Op: "open", Path: name, Err: e}
+	}
+	return fd, nil
+}
+
 // Forked from Golang but chooses to avoid performing lookup
 //
 // osMkdirAll creates a directory named path,
@@ -149,7 +165,7 @@ func parseDirEnt(buf []byte) (consumed int, name []byte, typ os.FileMode, err er
 // the directory itself, if the dirPath doesn't exist this function doesn't return
 // an error.
 func readDirFn(dirPath string, fn func(name string, typ os.FileMode) error) error {
-	f, err := OpenFile(dirPath, readMode, 0o666)
+	fd, err := openFileWithFD(dirPath, readMode, 0o666)
 	if err != nil {
 		if osErrToFileErr(err) == errFileNotFound {
 			return nil
@@ -160,15 +176,16 @@ func readDirFn(dirPath string, fn func(name string, typ os.FileMode) error) erro
 		// There may be permission error when dirPath
 		// is at the root of the disk mount that may
 		// not have the permissions to avoid 'noatime'
-		f, err = Open(dirPath)
+		fd, err = openFileWithFD(dirPath, os.O_RDONLY, 0o666)
 		if err != nil {
 			if osErrToFileErr(err) == errFileNotFound {
 				return nil
 			}
 			return osErrToFileErr(err)
 		}
+
 	}
-	defer f.Close()
+	defer syscall.Close(fd)
 
 	bufp := direntPool.Get().(*[]byte)
 	defer direntPool.Put(bufp)
@@ -181,7 +198,7 @@ func readDirFn(dirPath string, fn func(name string, typ os.FileMode) error) erro
 		if boff >= nbuf {
 			boff = 0
 			stop := globalOSMetrics.time(osMetricReadDirent)
-			nbuf, err = syscall.ReadDirent(int(f.Fd()), buf)
+			nbuf, err = syscall.ReadDirent(fd, buf)
 			stop()
 			if err != nil {
 				if isSysErrNotDir(err) {
@@ -241,7 +258,7 @@ func readDirFn(dirPath string, fn func(name string, typ os.FileMode) error) erro
 // Return count entries at the directory dirPath and all entries
 // if count is set to -1
 func readDirWithOpts(dirPath string, opts readDirOpts) (entries []string, err error) {
-	f, err := OpenFile(dirPath, readMode, 0o666)
+	fd, err := openFileWithFD(dirPath, readMode, 0o666)
 	if err != nil {
 		if !osIsPermission(err) {
 			return nil, osErrToFileErr(err)
@@ -249,12 +266,12 @@ func readDirWithOpts(dirPath string, opts readDirOpts) (entries []string, err er
 		// There may be permission error when dirPath
 		// is at the root of the disk mount that may
 		// not have the permissions to avoid 'noatime'
-		f, err = Open(dirPath)
+		fd, err = openFileWithFD(dirPath, os.O_RDONLY, 0o666)
 		if err != nil {
 			return nil, osErrToFileErr(err)
 		}
 	}
-	defer f.Close()
+	defer syscall.Close(fd)
 
 	bufp := direntPool.Get().(*[]byte)
 	defer direntPool.Put(bufp)
@@ -273,7 +290,7 @@ func readDirWithOpts(dirPath string, opts readDirOpts) (entries []string, err er
 		if boff >= nbuf {
 			boff = 0
 			stop := globalOSMetrics.time(osMetricReadDirent)
-			nbuf, err = syscall.ReadDirent(int(f.Fd()), buf)
+			nbuf, err = syscall.ReadDirent(fd, buf)
 			stop()
 			if err != nil {
 				if isSysErrNotDir(err) {

cmd/osmetric_string.go

@@ -14,23 +14,25 @@ func _() {
 	_ = x[osMetricRename-3]
 	_ = x[osMetricOpenFileW-4]
 	_ = x[osMetricOpenFileR-5]
-	_ = x[osMetricOpen-6]
+	_ = x[osMetricOpenFileWFd-6]
-	_ = x[osMetricOpenFileDirectIO-7]
+	_ = x[osMetricOpenFileRFd-7]
-	_ = x[osMetricLstat-8]
+	_ = x[osMetricOpen-8]
-	_ = x[osMetricRemove-9]
+	_ = x[osMetricOpenFileDirectIO-9]
-	_ = x[osMetricStat-10]
+	_ = x[osMetricLstat-10]
-	_ = x[osMetricAccess-11]
+	_ = x[osMetricRemove-11]
-	_ = x[osMetricCreate-12]
+	_ = x[osMetricStat-12]
-	_ = x[osMetricReadDirent-13]
+	_ = x[osMetricAccess-13]
-	_ = x[osMetricFdatasync-14]
+	_ = x[osMetricCreate-14]
-	_ = x[osMetricSync-15]
+	_ = x[osMetricReadDirent-15]
-	_ = x[osMetricRename2-16]
+	_ = x[osMetricFdatasync-16]
-	_ = x[osMetricLast-17]
+	_ = x[osMetricSync-17]
+	_ = x[osMetricRename2-18]
+	_ = x[osMetricLast-19]
 }
 
-const _osMetric_name = "RemoveAllMkdirAllMkdirRenameOpenFileWOpenFileROpenOpenFileDirectIOLstatRemoveStatAccessCreateReadDirentFdatasyncSyncRename2Last"
+const _osMetric_name = "RemoveAllMkdirAllMkdirRenameOpenFileWOpenFileROpenFileWFdOpenFileRFdOpenOpenFileDirectIOLstatRemoveStatAccessCreateReadDirentFdatasyncSyncRename2Last"
 
-var _osMetric_index = [...]uint8{0, 9, 17, 22, 28, 37, 46, 50, 66, 71, 77, 81, 87, 93, 103, 112, 116, 123, 127}
+var _osMetric_index = [...]uint8{0, 9, 17, 22, 28, 37, 46, 57, 68, 72, 88, 93, 99, 103, 109, 115, 125, 134, 138, 145, 149}
 
 func (i osMetric) String() string {
 	if i >= osMetric(len(_osMetric_index)-1) {