diff --git a/backports/configparser/__init__.py b/backports/configparser/__init__.py
index 1efa089..8789ad1 100644
--- a/backports/configparser/__init__.py
+++ b/backports/configparser/__init__.py
@@ -145,17 +145,18 @@
 
 from __future__ import annotations
 
-from collections.abc import MutableMapping
+# Do not import dataclasses; overhead is unacceptable (gh-117703)
+
+from collections.abc import Iterable, MutableMapping
 from collections import ChainMap as _ChainMap
 import contextlib
-from dataclasses import dataclass, field
 import functools
 from .compat import io
 import itertools
 import os
 import re
 import sys
-from typing import Iterable
+import types
 
 __all__ = (
     "NoSectionError",
@@ -578,28 +579,25 @@ def _interpolate_some(  # noqa: C901
                 )
 
 
-@dataclass
 class _ReadState:
-    elements_added: set[str] = field(default_factory=set)
-    cursect: dict[str, str] | None = None
-    sectname: str | None = None
-    optname: str | None = None
-    lineno: int = 0
-    indent_level: int = 0
-    errors: list[ParsingError] = field(default_factory=list)
-
+    elements_added : set[str]
+    cursect : dict[str, str] | None = None
+    sectname : str | None = None
+    optname : str | None = None
+    lineno : int = 0
+    indent_level : int = 0
+    errors : list[ParsingError]
 
-@dataclass
-class _Prefixes:
-    full: Iterable[str]
-    inline: Iterable[str]
+    def __init__(self):
+        self.elements_added = set()
+        self.errors = list()
 
 
 class _Line(str):
     def __new__(cls, val, *args, **kwargs):
         return super().__new__(cls, val)
 
-    def __init__(self, val, prefixes: _Prefixes):
+    def __init__(self, val, prefixes):
         self.prefixes = prefixes
 
     @functools.cached_property
@@ -705,8 +703,9 @@ def __init__(
             if allow_no_value:
                 self._optcre = re.compile(self._OPT_NV_TMPL.format(delim=d), re.VERBOSE)
             else:
-                self._optcre = re.compile(self._OPT_TMPL.format(delim=d), re.VERBOSE)
-        self._prefixes = _Prefixes(
+                self._optcre = re.compile(self._OPT_TMPL.format(delim=d),
+                                          re.VERBOSE)
+        self._prefixes = types.SimpleNamespace(
             full=tuple(comment_prefixes or ()),
             inline=tuple(inline_comment_prefixes or ()),
         )
diff --git a/tests/test_configparser.py b/tests/test_configparser.py
index 0d10ccd..dcafc30 100644
--- a/tests/test_configparser.py
+++ b/tests/test_configparser.py
@@ -1,7 +1,6 @@
 import collections
 import io
 import os
-import pathlib
 import textwrap
 import unittest
 
@@ -777,12 +776,12 @@ def test_read_returns_file_list(self):
         self.assertEqual(cf.get("Foo Bar", "foo"), "newbar")
         # check when we pass only a Path object:
         cf = self.newconfig()
-        parsed_files = cf.read(pathlib.Path(file1), encoding="utf-8")
+        parsed_files = cf.read(os_helper.FakePath(file1), encoding="utf-8")
         self.assertEqual(parsed_files, [file1])
         self.assertEqual(cf.get("Foo Bar", "foo"), "newbar")
         # check when we passed both a filename and a Path object:
         cf = self.newconfig()
-        parsed_files = cf.read([pathlib.Path(file1), file1], encoding="utf-8")
+        parsed_files = cf.read([os_helper.FakePath(file1), file1], encoding="utf-8")
         self.assertEqual(parsed_files, [file1, file1])
         self.assertEqual(cf.get("Foo Bar", "foo"), "newbar")
         # check when we pass only missing files: