vfs: log size of File and Dir in tests for optimization

vfs/file_test.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"os"
 	"testing"
+	"unsafe"
 
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/operations"
@@ -411,3 +412,7 @@ func TestFileRename(t *testing.T) {
 		})
 	}
 }
+
+func TestFileStructSize(t *testing.T) {
+	t.Logf("File struct has size %d bytes", unsafe.Sizeof(File{}))
+}