Certain methods that heap allocated subtypes inherit suffer a 50-80% performance penalty

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-08-13.19:36:41.892>
labels = ['expert-C-API', '3.9', 'performance']
title = 'Certain methods that heap allocated subtypes inherit suffer a 50-80% performance penalty'
updated_at = <Date 2020-02-28.08:02:38.315>
user = 'https://github.com/mr-nfamous'

bugs.python.org fields:

activity = <Date 2020-02-28.08:02:38.315>
actor = 'methane'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['C API']
creation = <Date 2018-08-13.19:36:41.892>
creator = 'bup'
dependencies = []
files = []
hgrepos = []
issue_num = 34396
keywords = ['patch']
message_count = 8.0
messages = ['323490', '323498', '328187', '339449', '339453', '339477', '348185', '362715']
nosy_count = 8.0
nosy_names = ['rhettinger', 'scoder', 'benjamin.peterson', 'methane', 'serhiy.storchaka', 'jdemeyer', 'bup', 'Marco Sulla']
pr_nums = ['14863']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue34396'
versions = ['Python 3.9']