gh-132042: Remove resolve_slotdups to speedup class creation #132156

sergey-miryanov · 2025-04-06T12:09:19Z

Removes resolve_slotdups.

Issue: Optimize class creation #132042

python-cla-bot · 2025-04-06T13:55:19Z

All commit authors signed the Contributor License Agreement.

StanFromIreland · 2025-04-06T17:08:31Z

Maybe take a look at this comment and have it in mind.

sergey-miryanov · 2025-04-06T17:17:11Z

@StanFromIreland Yeah, thanks! I just checked both scripts - and timing closely same. But I not finished main task, so results can changed.

Objects/typeobject.c

sergey-miryanov · 2025-04-09T08:05:08Z

Intermediate results:

Benchmark results (outdated)

Running Release|x64 interpreter...
Python 3.14.0a6+ (heads/gh-132042-optimize-class-creation:b0ad8754b45, Apr  9 2025, 11:38:25) [MSC v.1943 64 bit (AMD64)]

+----------------------------------------------------------------------------+---------+-----------------------+
| Benchmark                                                                  | ref     | new                   |
+============================================================================+=========+=======================+
| empty_cls-1000                                                             | 4.32 ms | 3.50 ms: 1.24x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_dunders-1000                                                      | 5.03 ms | 4.32 ms: 1.16x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| empty_cls_with_bases-1000-A, B                                             | 5.62 ms | 3.89 ms: 1.45x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_bases-1000-A, B                                                   | 6.18 ms | 4.62 ms: 1.34x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| empty_cls_with_bases-1000-A, B, D                                          | 6.37 ms | 4.18 ms: 1.52x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_bases-1000-A, B, D                                                | 6.81 ms | 4.92 ms: 1.39x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| empty_cls_with_bases-1000-A_with_dunders, B_with_dunders                   | 5.40 ms | 3.89 ms: 1.39x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_bases-1000-A_with_dunders, B_with_dunders                         | 6.08 ms | 4.66 ms: 1.31x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| empty_cls_with_bases-1000-A_with_dunders, B_with_dunders, D_with_dunders   | 6.08 ms | 4.24 ms: 1.44x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_bases-1000-A_with_dunders, B_with_dunders, D_with_dunders         | 6.79 ms | 5.01 ms: 1.36x faster |
+----------------------------------------------------------------------------+---------+-----------------------+
| empty_cls-100000                                                           | 436 ms  | 356 ms: 1.23x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_dunders-100000                                                    | 500 ms  | 434 ms: 1.15x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| empty_cls_with_bases-100000-A, B                                           | 563 ms  | 387 ms: 1.46x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_bases-100000-A, B                                                 | 612 ms  | 463 ms: 1.32x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| empty_cls_with_bases-100000-A, B, D                                        | 631 ms  | 418 ms: 1.51x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_bases-100000-A, B, D                                              | 683 ms  | 493 ms: 1.39x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| empty_cls_with_bases-100000-A_with_dunders, B_with_dunders                 | 545 ms  | 389 ms: 1.40x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_bases-100000-A_with_dunders, B_with_dunders                       | 607 ms  | 467 ms: 1.30x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| empty_cls_with_bases-100000-A_with_dunders, B_with_dunders, D_with_dunders | 609 ms  | 423 ms: 1.44x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| cls_with_bases-100000-A_with_dunders, B_with_dunders, D_with_dunders       | 679 ms  | 502 ms: 1.35x faster  |
+----------------------------------------------------------------------------+---------+-----------------------+
| Geometric mean                                                             | (ref)   | 1.35x faster          |
+----------------------------------------------------------------------------+---------+-----------------------+

b.txt

sergey-miryanov · 2025-04-09T18:49:31Z

I added tests from gh-76527 (script for testing with pyperf b.txt):

empty_cls - tests for classes without any methods
cls - tests for classes with few dunder methods
bases - with suffix _dun - base classes with few dunder methods

Benchmark results (outdated)

+---------------------------------------------------------------+----------+-----------------------+
| Benchmark                                                     | ref      | new                   |
+===============================================================+==========+=======================+
| 1000-empty_cls                                                | 4.42 ms  | 3.50 ms: 1.26x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_dunders                                         | 5.25 ms  | 4.45 ms: 1.18x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A', 'B']                    | 5.70 ms  | 3.84 ms: 1.48x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['A', 'B']                          | 6.26 ms  | 4.62 ms: 1.35x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A', 'B', 'D']               | 6.49 ms  | 4.16 ms: 1.56x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['A', 'B', 'D']                     | 6.97 ms  | 4.94 ms: 1.41x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A_dun', 'B_dun']            | 5.52 ms  | 3.89 ms: 1.42x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['A_dun', 'B_dun']                  | 6.21 ms  | 4.67 ms: 1.33x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A_dun', 'B_dun', 'D_dun']   | 6.20 ms  | 4.20 ms: 1.47x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['A_dun', 'B_dun', 'D_dun']         | 7.10 ms  | 5.02 ms: 1.42x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['Logger']                    | 5.42 ms  | 4.22 ms: 1.28x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['Logger']                          | 6.05 ms  | 5.08 ms: 1.19x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['DatagramHandler']           | 6.63 ms  | 4.42 ms: 1.50x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['DatagramHandler']                 | 7.23 ms  | 5.24 ms: 1.38x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['MagicMock']                 | 7.66 ms  | 4.95 ms: 1.55x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['MagicMock']                       | 8.26 ms  | 5.74 ms: 1.44x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['Shelf']                     | 9.46 ms  | 6.86 ms: 1.38x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['Shelf']                           | 10.2 ms  | 7.84 ms: 1.30x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['tuple']                     | 5.62 ms  | 4.18 ms: 1.35x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['tuple']                           | 6.33 ms  | 5.53 ms: 1.14x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['dict']                      | 5.60 ms  | 4.90 ms: 1.14x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['dict']                            | 6.30 ms  | 5.56 ms: 1.13x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-empty_cls_with_bases-bases=['list']                      | 5.99 ms  | 4.74 ms: 1.26x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 1000-cls_with_bases-bases=['list']                            | 6.68 ms  | 5.64 ms: 1.19x faster |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls                                              | 447 ms   | 354 ms: 1.26x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_dunders                                       | 510 ms   | 436 ms: 1.17x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['A', 'B']                  | 569 ms   | 392 ms: 1.45x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['A', 'B']                        | 631 ms   | 470 ms: 1.34x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['A', 'B', 'D']             | 644 ms   | 416 ms: 1.55x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['A', 'B', 'D']                   | 702 ms   | 499 ms: 1.41x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['A_dun', 'B_dun']          | 550 ms   | 387 ms: 1.42x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['A_dun', 'B_dun']                | 627 ms   | 474 ms: 1.32x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['A_dun', 'B_dun', 'D_dun'] | 621 ms   | 422 ms: 1.47x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['A_dun', 'B_dun', 'D_dun']       | 694 ms   | 509 ms: 1.36x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['Logger']                  | 540 ms   | 418 ms: 1.29x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['Logger']                        | 612 ms   | 508 ms: 1.20x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['DatagramHandler']         | 657 ms   | 441 ms: 1.49x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['DatagramHandler']               | 726 ms   | 530 ms: 1.37x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['MagicMock']               | 764 ms   | 492 ms: 1.55x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['MagicMock']                     | 828 ms   | 580 ms: 1.43x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['Shelf']                   | 954 ms   | 689 ms: 1.39x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['Shelf']                         | 1.04 sec | 784 ms: 1.33x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['tuple']                   | 558 ms   | 417 ms: 1.34x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['tuple']                         | 649 ms   | 502 ms: 1.29x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['dict']                    | 579 ms   | 464 ms: 1.25x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['dict']                          | 648 ms   | 547 ms: 1.19x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-empty_cls_with_bases-bases=['list']                    | 630 ms   | 476 ms: 1.32x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| 100000-cls_with_bases-bases=['list']                          | 686 ms   | 563 ms: 1.22x faster  |
+---------------------------------------------------------------+----------+-----------------------+
| Geometric mean                                                | (ref)    | 1.34x faster          |
+---------------------------------------------------------------+----------+-----------------------+

Also benchgcclasses2.py output:
ref:

➜ .\python.bat ..\cpython-issues\gh-132042-optimize-class-creation\benchgcclasses2.py
Running Release|x64 interpreter...
GC time: 93.8 ms
gc: collecting generation 2...
gc: objects in each generation: 0 0 905261
gc: objects in permanent generation: 0

➜ .\python.bat ..\cpython-issues\gh-132042-optimize-class-creation\benchgcclasses2.py
Running Release|x64 interpreter...
GC time: 125.0 ms
gc: collecting generation 2...
gc: objects in each generation: 0 0 905261
gc: objects in permanent generation: 0
RSS:

new:

➜ .\python.bat ..\cpython-issues\gh-132042-optimize-class-creation\benchgcclasses2.py
Running Release|x64 interpreter...
GC time: 109.4 ms
gc: collecting generation 2...
gc: objects in each generation: 0 0 905262
gc: objects in permanent generation: 0
RSS:

➜ .\python.bat ..\cpython-issues\gh-132042-optimize-class-creation\benchgcclasses2.py
Running Release|x64 interpreter...
GC time: 125.0 ms
gc: collecting generation 2...
gc: objects in each generation: 0 0 905262
gc: objects in permanent generation: 0
RSS:

Time varies, I'm not sure it is statistically significant. Count of objects closely the same.

Async import time (➜ .\python.bat -X importtime -c 'import asyncio'):
ref:

import time:      1116 |      86283 | asyncio

new:

import time:      1014 |      82194 | asyncio

…solve_slotdups

sergey-miryanov · 2025-04-09T20:33:37Z

Remove resolve_slotdups (new2):

Benchmark results (outdated)

+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| Benchmark                                                   | ref     | new                   | new2                  |
+=============================================================+=========+=======================+=======================+
| 1000-empty_cls                                              | 4.42 ms | 3.50 ms: 1.26x faster | 3.37 ms: 1.31x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_dunders                                       | 5.25 ms | 4.45 ms: 1.18x faster | 4.38 ms: 1.20x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A', 'B']                  | 5.70 ms | 3.84 ms: 1.48x faster | 3.68 ms: 1.55x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['A', 'B']                        | 6.26 ms | 4.62 ms: 1.35x faster | 4.51 ms: 1.39x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A', 'B', 'D']             | 6.49 ms | 4.16 ms: 1.56x faster | 4.00 ms: 1.62x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['A', 'B', 'D']                   | 6.97 ms | 4.94 ms: 1.41x faster | 4.80 ms: 1.45x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A_dun', 'B_dun']          | 5.52 ms | 3.89 ms: 1.42x faster | 3.74 ms: 1.48x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['A_dun', 'B_dun']                | 6.21 ms | 4.67 ms: 1.33x faster | 4.55 ms: 1.36x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A_dun', 'B_dun', 'D_dun'] | 6.20 ms | 4.20 ms: 1.47x faster | 4.08 ms: 1.52x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['A_dun', 'B_dun', 'D_dun']       | 7.10 ms | 5.02 ms: 1.42x faster | 4.89 ms: 1.45x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['Logger']                  | 5.42 ms | 4.22 ms: 1.28x faster | 4.06 ms: 1.33x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['Logger']                        | 6.05 ms | 5.08 ms: 1.19x faster | 4.97 ms: 1.22x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['DatagramHandler']         | 6.63 ms | 4.42 ms: 1.50x faster | 4.26 ms: 1.56x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['DatagramHandler']               | 7.23 ms | 5.24 ms: 1.38x faster | 5.09 ms: 1.42x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['MagicMock']               | 7.66 ms | 4.95 ms: 1.55x faster | 4.83 ms: 1.59x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['MagicMock']                     | 8.26 ms | 5.74 ms: 1.44x faster | 5.64 ms: 1.46x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['Shelf']                   | 9.46 ms | 6.86 ms: 1.38x faster | 6.67 ms: 1.42x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['Shelf']                         | 10.2 ms | 7.84 ms: 1.30x faster | 7.62 ms: 1.34x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['tuple']                   | 5.62 ms | 4.18 ms: 1.35x faster | 3.82 ms: 1.47x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['tuple']                         | 6.33 ms | 5.53 ms: 1.14x faster | 4.57 ms: 1.39x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['dict']                    | 5.60 ms | 4.90 ms: 1.14x faster | 4.32 ms: 1.30x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['dict']                          | 6.30 ms | 5.56 ms: 1.13x faster | 5.15 ms: 1.22x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-empty_cls_with_bases-bases=['list']                    | 5.99 ms | 4.74 ms: 1.26x faster | 4.39 ms: 1.36x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| 1000-cls_with_bases-bases=['list']                          | 6.68 ms | 5.64 ms: 1.19x faster | 5.18 ms: 1.29x faster |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+
| Geometric mean                                              | (ref)   | 1.34x faster          | 1.40x faster          |
+-------------------------------------------------------------+---------+-----------------------+-----------------------+

…d_objects

sergey-miryanov · 2025-04-09T20:55:11Z

It is ready to review. Please take a look.

Objects/typeobject.c

Include/cpython/descrobject.h

Co-authored-by: Victor Stinner <vstinner@python.org>

To get update from main

sergey-miryanov · 2025-05-12T13:41:04Z

The following tests call update_one_slot (via fixup_slot_dispatchers or update_slot) and may be affected by this PR.

test	warmup calls x slotdefs count	loop calls x slotdefs count	result (base vs pr)
bench_mp_pool	27	0	1.01x faster (82.8 ms / 81.7 ms)
bench_thread_pool	25	0	1.01x slower (887 us / 891 us)
deepcopy_reduce	0	1	1.02x slower (2.73 us / 2.78 us)
docutils	347	0	not significant
dulwich_log	3	0	1.01x slower (59.7 ms / 60.1 ms)
genshi_text	9	0	1.00x slower (21.0 ms / 21.1 ms)
genshi_xml	9	0	1.01x slower (49.2 ms / 49.6 ms)
html5lib	33	0	1.04x slower (60.0 ms / 62.6 ms)
pprint_pformat	196	0	1.01x faster (1.50 sec / 1.49 sec)
pylint	883	7	not significant
regex_v8	4	0	1.05x faster (23.6 ms / 22.5 ms)
sympy_expand	33	0	not significant
sympy_integrate	39	0	not significant
sympy_sum	39	1	1.01x slower (149 ms / 150 ms)
sympy_str	30	0	1.00x slower (268 ms / 269 ms)
typing_runtime_protocols	187	0	1.01x slower (168 us / 169 us)
xml_etree_parse	6	0	1.04x faster (147 ms / 141 ms)
xml_etree_iterparse	26	20	not significant
xml_etree_generate	6	0	1.01x faster (86.9 ms / 85.9 ms)
xml_etree_process	6	0	not significant

As can be seen most of the calls come from warmup iteration and shouldn't be counted in the results. Only the following tests call update_one_slot from inside loop iterations. pylint and xml_etree_iterparse have more calls than the other two tests but have 'not significant' results.

IMHO this set of benchmarks is not suitable to show the differences made by this PR.

sergey-miryanov · 2025-06-24T19:33:10Z

Fixed merge conflicts.

Updated results:

Geometric mean - 1.12x faster

+-------------------------------------------------------------+---------+-----------------------+
| Benchmark                                                   | ref     | dups                  |
+=============================================================+=========+=======================+
| 1000-empty_cls                                              | 4.35 ms | 3.80 ms: 1.15x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_dunders                                       | 5.05 ms | 4.55 ms: 1.11x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A', 'B']                  | 5.58 ms | 4.93 ms: 1.13x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['A', 'B']                        | 6.15 ms | 5.71 ms: 1.08x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A', 'B', 'D']             | 6.34 ms | 5.67 ms: 1.12x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['A', 'B', 'D']                   | 6.82 ms | 6.35 ms: 1.07x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A_dun', 'B_dun']          | 5.39 ms | 4.89 ms: 1.10x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['A_dun', 'B_dun']                | 6.11 ms | 5.67 ms: 1.08x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['A_dun', 'B_dun', 'D_dun'] | 6.07 ms | 5.54 ms: 1.09x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['A_dun', 'B_dun', 'D_dun']       | 6.84 ms | 6.37 ms: 1.07x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['Logger']                  | 5.30 ms | 4.74 ms: 1.12x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['Logger']                        | 5.92 ms | 5.47 ms: 1.08x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['DatagramHandler']         | 6.40 ms | 6.06 ms: 1.06x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['DatagramHandler']               | 7.03 ms | 6.63 ms: 1.06x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['MagicMock']               | 7.33 ms | 6.99 ms: 1.05x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['MagicMock']                     | 7.96 ms | 7.72 ms: 1.03x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['Shelf']                   | 9.40 ms | 8.92 ms: 1.05x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['Shelf']                         | 9.94 ms | 9.70 ms: 1.02x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['tuple']                   | 5.56 ms | 4.31 ms: 1.29x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['tuple']                         | 6.23 ms | 5.26 ms: 1.18x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['dict']                    | 5.56 ms | 4.50 ms: 1.24x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['dict']                          | 6.18 ms | 5.29 ms: 1.17x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-empty_cls_with_bases-bases=['list']                    | 5.99 ms | 4.45 ms: 1.34x faster |
+-------------------------------------------------------------+---------+-----------------------+
| 1000-cls_with_bases-bases=['list']                          | 6.54 ms | 5.28 ms: 1.24x faster |
+-------------------------------------------------------------+---------+-----------------------+
| Geometric mean                                              | (ref)   | 1.12x faster          |
+-------------------------------------------------------------+---------+-----------------------+

Include/internal/pycore_typeobject.h

Objects/typeobject.c

Co-authored-by: Kumar Aditya <kumaraditya@python.org> Co-authored-by: Victor Stinner <vstinner@python.org>

…sergey-miryanov/cpython into pythongh-132042-optimize-class-creation

sergey-miryanov · 2025-10-01T19:18:49Z

@kumaraditya303 @vstinner Thanks for review!

I will be able to run benchmarks after updates on this weekends (now on traveling laptop).

vstinner

LGTM. A few coding style suggestions.

Objects/typeobject.c

Co-authored-by: Victor Stinner <vstinner@python.org>

Objects/typeobject.c

Co-authored-by: Kumar Aditya <kumaraditya@python.org>

kumaraditya303

Nice improvement!

sergey-miryanov · 2025-10-03T07:55:06Z

@kumaraditya303 thanks!

vstinner · 2025-10-03T09:56:54Z

Micro-benchmark on creating on empty class:

python -m pyperf timeit 'class A: pass'

Result: Mean +- std dev: [ref] 9.92 us +- 0.09 us -> [change] 8.47 us +- 0.10 us: 1.17x faster.

vstinner · 2025-10-03T09:58:37Z

Merged. Thank you, that's a nice performance enhancement!

bedevere-bot · 2025-10-03T10:33:53Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Debian root 3.x (tier-1) has failed when building commit e6e376a.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/345/builds/12336) and take a look at the build logs.
Check if the failure is related to this commit (e6e376a) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/345/builds/12336

Failed tests:

test.test_multiprocessing_forkserver.test_processes
test.test_multiprocessing_spawn.test_misc
test.test_multiprocessing_forkserver.test_misc

Failed subtests:

test_large_pool - test.test_multiprocessing_spawn.test_misc.MiscTestCase.test_large_pool
test_many_processes - test.test_multiprocessing_forkserver.test_processes.WithProcessesTestProcess.test_many_processes

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/process.py", line 320, in _bootstrap
    self.run()
    ~~~~~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 523, in _sleep_some_event
    event.set()
    ~~~~~~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 344, in set
    with self._cond:
         ^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 242, in __exit__
    return self._lock.__exit__(*args)
           ~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 100, in __exit__
    return self._semlock.__exit__(*args)
           ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
KeyboardInterrupt
k


Traceback (most recent call last):
  File "<string>", line 1, in <module>
    from multiprocessing.forkserver import main; main(9, 10, ['__main__', 'test.test_multiprocessing_forkserver'], **{'sys_path': ['/root/buildarea/3.x.angelico-debian-amd64/build', '/root/buildarea/3.x.angelico-debian-amd64/build/target/lib/python315.zip', '/root/buildarea/3.x.angelico-debian-amd64/build/Lib', '/root/buildarea/3.x.angelico-debian-amd64/build/build/lib.linux-x86_64-3.15', '/root/.local/lib/python3.15/site-packages'], 'authkey_r': 12})
                                                 ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 329, in main
    pid = os.fork()
OSError: [Errno 12] Cannot allocate memory
ERROR


Traceback (most recent call last):
  File "<string>", line 1, in <module>
    from multiprocessing.forkserver import main; main(10, 11, ['__main__'], **{'sys_path': ['/root/buildarea/3.x.angelico-debian-amd64/build/target/lib/python315.zip', '/root/buildarea/3.x.angelico-debian-amd64/build/Lib', '/root/buildarea/3.x.angelico-debian-amd64/build/build/lib.linux-x86_64-3.15'], 'main_path': '/root/buildarea/3.x.angelico-debian-amd64/build/build/test_python_1406154æ/@test_1406154_tmpæ', 'authkey_r': 13})
                                                 ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 329, in main
    pid = os.fork()
OSError: [Errno 12] Cannot allocate memory
Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/build/test_python_1406154æ/@test_1406154_tmpæ", line 4, in <module>
    with multiprocessing.Pool(200) as p:
         ~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/context.py", line 119, in Pool
    return Pool(processes, initializer, initargs, maxtasksperchild,
                context=self.get_context())
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/pool.py", line 215, in __init__
    self._repopulate_pool()
    ~~~~~~~~~~~~~~~~~~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/pool.py", line 306, in _repopulate_pool
    return self._repopulate_pool_static(self._ctx, self.Process,
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
                                        self._processes,
                                        ^^^^^^^^^^^^^^^^
    ...<3 lines>...
                                        self._maxtasksperchild,
                                        ^^^^^^^^^^^^^^^^^^^^^^^
                                        self._wrap_exception)
                                        ^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/pool.py", line 329, in _repopulate_pool_static
    w.start()
    ~~~~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
                  ~~~~~~~~~~~^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/context.py", line 300, in _Popen
    return Popen(process_obj)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_forkserver.py", line 35, in __init__
    super().__init__(process_obj)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_fork.py", line 20, in __init__
    self._launch(process_obj)
    ~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_forkserver.py", line 59, in _launch
    self.pid = forkserver.read_signed(self.sentinel)
               ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 395, in read_signed
    raise EOFError('unexpected EOF')
EOFError: unexpected EOF
Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 340, in main
    code = _serve_one(child_r, fds,
                      unused_fds,
                      old_handlers)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 380, in _serve_one
    code = spawn._main(child_r, parent_sentinel)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/spawn.py", line 132, in _main
    self = reduction.pickle.load(from_parent)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 117, in __setstate__
    self._semlock = _multiprocessing.SemLock._rebuild(*state)
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory
Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 340, in main
    code = _serve_one(child_r, fds,
                      unused_fds,
                      old_handlers)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 380, in _serve_one
    code = spawn._main(child_r, parent_sentinel)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/spawn.py", line 132, in _main
    self = reduction.pickle.load(from_parent)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 117, in __setstate__
    self._semlock = _multiprocessing.SemLock._rebuild(*state)
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory
Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 340, in main
    code = _serve_one(child_r, fds,
                      unused_fds,
                      old_handlers)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 380, in _serve_one
    code = spawn._main(child_r, parent_sentinel)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/spawn.py", line 132, in _main
    self = reduction.pickle.load(from_parent)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 117, in __setstate__
    self._semlock = _multiprocessing.SemLock._rebuild(*state)
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory
Traceback (most recent call last):
Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 340, in main
    code = _serve_one(child_r, fds,
                      unused_fds,
                      old_handlers)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 340, in main
    code = _serve_one(child_r, fds,
                      unused_fds,
                      old_handlers)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 380, in _serve_one
    code = spawn._main(child_r, parent_sentinel)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/spawn.py", line 132, in _main
    self = reduction.pickle.load(from_parent)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 117, in __setstate__
    self._semlock = _multiprocessing.SemLock._rebuild(*state)
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory
Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 340, in main
    code = _serve_one(child_r, fds,
                      unused_fds,
                      old_handlers)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 380, in _serve_one
    code = spawn._main(child_r, parent_sentinel)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/spawn.py", line 132, in _main
    self = reduction.pickle.load(from_parent)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 117, in __setstate__
    self._semlock = _multiprocessing.SemLock._rebuild(*state)
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 380, in _serve_one
    code = spawn._main(child_r, parent_sentinel)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/spawn.py", line 132, in _main
    self = reduction.pickle.load(from_parent)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 117, in __setstate__
    self._semlock = _multiprocessing.SemLock._rebuild(*state)
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory
Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 340, in main
    code = _serve_one(child_r, fds,
                      unused_fds,
                      old_handlers)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 380, in _serve_one
    code = spawn._main(child_r, parent_sentinel)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/spawn.py", line 132, in _main
    self = reduction.pickle.load(from_parent)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/synchronize.py", line 117, in __setstate__
    self._semlock = _multiprocessing.SemLock._rebuild(*state)
                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory
---


Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 7021, in test_large_pool
    rc, out, err = script_helper.assert_python_ok(testfn)
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 182, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 167, in _assert_python
    res.fail(cmd_line)
    ~~~~~~~~^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 80, in fail
    raise AssertionError(f"Process return code is {exitcode}\n"
    ...<10 lines>...
                         f"---")
AssertionError: Process return code is 1
command line: ['/root/buildarea/3.x.angelico-debian-amd64/build/python', '-X', 'faulthandler', '-I', '@test_1406154_tmpæ']


Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/contextlib.py", line 85, in inner
    return func(*args, **kwds)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 761, in test_many_processes
    p.start()
    ~~~~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
                  ~~~~~~~~~~~^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/context.py", line 300, in _Popen
    return Popen(process_obj)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_forkserver.py", line 35, in __init__
    super().__init__(process_obj)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_fork.py", line 20, in __init__
    self._launch(process_obj)
    ~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_forkserver.py", line 59, in _launch
    self.pid = forkserver.read_signed(self.sentinel)
               ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 395, in read_signed
    raise EOFError('unexpected EOF')
EOFError: unexpected EOF


Traceback (most recent call last):
  File "<string>", line 1, in <module>
    from multiprocessing.forkserver import main; main(10, 11, ['__main__'], **{'sys_path': ['/root/buildarea/3.x.angelico-debian-amd64/build/target/lib/python315.zip', '/root/buildarea/3.x.angelico-debian-amd64/build/Lib', '/root/buildarea/3.x.angelico-debian-amd64/build/build/lib.linux-x86_64-3.15'], 'main_path': '/root/buildarea/3.x.angelico-debian-amd64/build/build/test_python_1434974æ/@test_1434974_tmpæ', 'authkey_r': 13})
                                                 ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 329, in main
    pid = os.fork()
OSError: [Errno 12] Cannot allocate memory
Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/build/test_python_1434974æ/@test_1434974_tmpæ", line 4, in <module>
    with multiprocessing.Pool(200) as p:
         ~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/context.py", line 119, in Pool
    return Pool(processes, initializer, initargs, maxtasksperchild,
                context=self.get_context())
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/pool.py", line 215, in __init__
    self._repopulate_pool()
    ~~~~~~~~~~~~~~~~~~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/pool.py", line 306, in _repopulate_pool
    return self._repopulate_pool_static(self._ctx, self.Process,
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
                                        self._processes,
                                        ^^^^^^^^^^^^^^^^
    ...<3 lines>...
                                        self._maxtasksperchild,
                                        ^^^^^^^^^^^^^^^^^^^^^^^
                                        self._wrap_exception)
                                        ^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/pool.py", line 329, in _repopulate_pool_static
    w.start()
    ~~~~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
                  ~~~~~~~~~~~^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/context.py", line 300, in _Popen
    return Popen(process_obj)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_forkserver.py", line 35, in __init__
    super().__init__(process_obj)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_fork.py", line 20, in __init__
    self._launch(process_obj)
    ~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_forkserver.py", line 59, in _launch
    self.pid = forkserver.read_signed(self.sentinel)
               ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 395, in read_signed
    raise EOFError('unexpected EOF')
EOFError: unexpected EOF
---


Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 7021, in test_large_pool
    rc, out, err = script_helper.assert_python_ok(testfn)
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 182, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 167, in _assert_python
    res.fail(cmd_line)
    ~~~~~~~~^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 80, in fail
    raise AssertionError(f"Process return code is {exitcode}\n"
    ...<10 lines>...
                         f"---")
AssertionError: Process return code is 1
command line: ['/root/buildarea/3.x.angelico-debian-amd64/build/python', '-X', 'faulthandler', '-I', '@test_1434974_tmpæ']

sobolevn · 2025-10-03T10:53:44Z

Congrats, very useful speedup!

sergey-miryanov added 2 commits April 6, 2025 17:08

Prebuild mro_dict for find_name_in_mro

56d13fc

Preget tp_dict

1eed75d

bedevere-app bot mentioned this pull request Apr 6, 2025

Optimize class creation #132042

Open

Slotdefs cache

bba66d6

sergey-miryanov commented Apr 7, 2025

View reviewed changes

Objects/typeobject.c Outdated Show resolved Hide resolved

AA-Turner added the interpreter-core (Objects, Python, Grammar, and Parser dirs) label Apr 7, 2025

sergey-miryanov added 4 commits April 9, 2025 00:43

Move slotdefs_cache to interp

bac95a5

Use bytes for slotdefs_cache

8d1f5be

Use type_slots_ptrs cache

8cf19e8

Move slotdefs_cache init to pycore_init_builtins

b0ad875

sergey-miryanov added 3 commits April 10, 2025 00:22

Create slotdefs_cache only for main interpreter

79a165d

Do not iterate slotdefs_cache just check dups count

a853294

Add name_count to pytype_slotdef and get rid of slotdefs_cache and re…

75c17fb

…solve_slotdups

sergey-miryanov added 3 commits April 10, 2025 01:36

Rename _PyType_InitSlotDefsCache to _PyType_InitSlotDefsNameCounts

fc17a68

Get rid of type_slots_ptrs and type_slots_pname from _Py_interp_cache…

736bca4

…d_objects

Add news entry

1341ed9

sergey-miryanov marked this pull request as ready for review April 9, 2025 20:54

sergey-miryanov requested review from ericsnowcurrently and markshannon as code owners April 9, 2025 20:54

bedevere-app bot added the awaiting review label Apr 9, 2025

sergey-miryanov mentioned this pull request Apr 10, 2025

gh-127266: avoid data races when updating type slots #131174

Merged

vstinner reviewed Apr 15, 2025

View reviewed changes

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Objects/typeobject.c Outdated Show resolved Hide resolved

Objects/typeobject.c Outdated Show resolved Hide resolved

Objects/typeobject.c Show resolved Hide resolved

Include/cpython/descrobject.h Outdated Show resolved Hide resolved

Rename _PyType_InitSlotDefsNameCounts

3efb9ca

Co-authored-by: Victor Stinner <vstinner@python.org>

Merge branch 'main' into pythongh-132042-optimize-class-creation

05df484

To get update from main

Merge branch 'main' into pythongh-132042-optimize-class-creation

7a61ed3

sergey-miryanov requested a review from ZeroIntensity as a code owner June 24, 2025 19:32

kumaraditya303 reviewed Oct 1, 2025

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kumaraditya303 reviewed Oct 1, 2025

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kumaraditya303 reviewed Oct 1, 2025

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vstinner reviewed Oct 1, 2025

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sergey-miryanov and others added 4 commits October 1, 2025 23:41

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211d043

Co-authored-by: Kumar Aditya <kumaraditya@python.org> Co-authored-by: Victor Stinner <vstinner@python.org>

Merge branch 'pythongh-132042-optimize-class-creation' of github.com:…

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…sergey-miryanov/cpython into pythongh-132042-optimize-class-creation

Fix stray change

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Merge branch 'main' into pythongh-132042-optimize-class-creation

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Fix news entry

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vstinner approved these changes Oct 2, 2025

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sergey-miryanov and others added 2 commits October 2, 2025 23:36

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Co-authored-by: Victor Stinner <vstinner@python.org>

Fix build

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kumaraditya303 reviewed Oct 3, 2025

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Update Objects/typeobject.c

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Co-authored-by: Kumar Aditya <kumaraditya@python.org>

kumaraditya303 approved these changes Oct 3, 2025

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vstinner merged commit e6e376a into python:main Oct 3, 2025
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gh-132042: Remove resolve_slotdups to speedup class creation #132156

gh-132042: Remove resolve_slotdups to speedup class creation #132156

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