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Benchmark results (outdated)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 <[email protected]>

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 <[email protected]> Co-authored-by: Victor Stinner <[email protected]>

…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 <[email protected]>

Objects/typeobject.c

Co-authored-by: Kumar Aditya <[email protected]>

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 · 2025-10-03T18:06:12Z

Thanks everyone!

…ython#132156) Co-authored-by: Victor Stinner <[email protected]> Co-authored-by: sobolevn <[email protected]> Co-authored-by: Kumar Aditya <[email protected]>

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

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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

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Rename _PyType_InitSlotDefsNameCounts

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Co-authored-by: Victor Stinner <[email protected]>

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

7a61ed3

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

Apply suggestions from code review

211d043

Co-authored-by: Kumar Aditya <[email protected]> Co-authored-by: Victor Stinner <[email protected]>

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

82466cc

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Fix build

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kumaraditya303 reviewed Oct 3, 2025

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Update Objects/typeobject.c

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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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