diff --git a/benchmark.py b/benchmark.py
index 4e1a975..4b38dd9 100644
--- a/benchmark.py
+++ b/benchmark.py
@@ -123,25 +123,82 @@ def get_tree_size(path):
     try:
         for entry in scandir.scandir(path):
             if entry.is_dir(follow_symlinks=False):
-                size += get_tree_size(os.path.join(path, entry.name))
+                size += get_tree_size(entry.path)
             else:
                 size += entry.stat(follow_symlinks=False).st_size
     except OSError:
         pass
     return size
 
+def get_tree_size_listdir(path):
+    """Return total size of all files in directory tree at path."""
+    size = 0
+    try:
+        for name in os.listdir(path):
+            fullpath = os.path.join(path, name)
+            if os.path.isdir(fullpath) and not os.path.islink(fullpath):
+                size += get_tree_size_listdir(fullpath)
+            else:
+                size += os.stat(fullpath, follow_symlinks=False).st_size
+    except OSError:
+        pass
+    return size
+
+def get_tree_size_listdir_stat(path):
+    """Return total size of all files in directory tree at path."""
+    size = 0
+    try:
+        for name in os.listdir(path):
+            fullpath = os.path.join(path, name)
+            st = os.stat(fullpath, follow_symlinks=False)
+            if stat.S_ISDIR(st.st_mode):
+                size += get_tree_size_listdir_stat(fullpath)
+            else:
+                size += st.st_size
+    except OSError:
+        pass
+    return size
+
+if hasattr(os, 'fwalk'):
+    _dir_flags = os.O_RDONLY
+    def get_tree_size_listdir_fd(fd):
+        """Return total size of all files in directory tree at path."""
+        size = 0
+        try:
+            for name in os.listdir(fd):
+                st = os.stat(name, follow_symlinks=False, dir_fd=fd)
+                if stat.S_ISDIR(st.st_mode):
+                    top_fd = os.open(name, _dir_flags, dir_fd=fd)
+                    try:
+                        size += get_tree_size_listdir_fd(top_fd)
+                    finally:
+                        os.close(top_fd)
+                else:
+                    size += st.st_size
+        except OSError:
+            pass
+        return size
 
 def benchmark(path, get_size=False):
     sizes = {}
 
     if get_size:
-        def do_os_walk():
-            size = 0
-            for root, dirs, files in os_walk_func(path):
-                for filename in files:
-                    fullname = os.path.join(root, filename)
-                    size += os.path.getsize(fullname)
-            sizes['os_walk'] = size
+        if get_size == 'fd' or (hasattr(os, 'fwalk') and get_size == 'best'):
+            print('Comparing against get_tree_size_listdir_fd')
+            def do_os_walk():
+                fd = os.open(path, _dir_flags)
+                try:
+                    sizes['os_walk'] = get_tree_size_listdir_fd(fd)
+                finally:
+                    os.close(fd)
+        elif get_size == 'stat':
+            print('Comparing against get_tree_size_listdir_stat')
+            def do_os_walk():
+                sizes['os_walk'] = get_tree_size_listdir_stat(path)
+        else:
+            print('Comparing against get_tree_size_listdir')
+            def do_os_walk():
+                sizes['os_walk'] = get_tree_size_listdir(path)
 
         def do_scandir_walk():
             sizes['scandir_walk'] = get_tree_size(path)
@@ -195,6 +252,8 @@ using it instead of creating a tree."""
                       help='version of scandir() to use, default "%default"')
     parser.add_option('-o', '--os-walk', type='choice', choices=['match', 'builtin', 'python'], default='builtin',
                       help='version of os.walk() to use, default "%default"')
+    parser.add_option('--get-size-type', type='choice', choices=['best', 'stat', 'fd', 'isdir'], default='best',
+                      help='version of get_tree_size_listdir_*() to use, default "%default"')
     options, args = parser.parse_args()
 
     if args:
@@ -252,4 +311,4 @@ using it instead of creating a tree."""
     else:
         print('Comparing against ctypes emulation of os.walk()')
 
-    benchmark(tree_dir, get_size=options.size)
+    benchmark(tree_dir, get_size=options.size and options.get_size_type)