gh-118761: Improve import time by lazy import of traceback

[donBarbos]

TODO:

• Improve import time modules by lazy import traceback
• Remove unused import fcntl

CPython configure flags:

./configure --enable-optimizations --with-lto --enable-loadable-sqlite-extensions

Hyperfine benchmark for import traceback:

$ hyperfine --warmup 11 "./python -c 'import traceback'"
Benchmark 1: ./python -c 'import traceback'
  Time (mean ± σ):      17.0 ms ±   0.5 ms    [User: 14.2 ms, System: 2.7 ms]
  Range (min … max):    16.5 ms …  22.7 ms    167 runs

Hyperfine benchmarks for updated modules:

import _pyrepl experiments (no diff)

➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 --runs 3000 "./python -c 'import _pyrepl'"
Benchmark 1: ./python -c 'import _pyrepl'
  Time (mean ± σ):       9.2 ms ±   0.4 ms    [User: 7.3 ms, System: 1.8 ms]
  Range (min … max):     8.6 ms …  14.7 ms    3000 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 --runs 3000 "./python -c 'import _pyrepl'"
Benchmark 1: ./python -c 'import _pyrepl'
  Time (mean ± σ):       9.3 ms ±   0.3 ms    [User: 7.4 ms, System: 1.8 ms]
  Range (min … max):     8.7 ms …  14.7 ms    3000 runs

import code experiments

➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 --runs 3000 "./python -c 'import code'"
Benchmark 1: ./python -c 'import code'
  Time (mean ± σ):      10.0 ms ±   0.5 ms    [User: 8.2 ms, System: 1.8 ms]
  Range (min … max):     9.3 ms …  15.8 ms    3000 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 --runs 3000 "./python -c 'import code'"
Benchmark 1: ./python -c 'import code'
  Time (mean ± σ):      17.8 ms ±   0.8 ms    [User: 14.9 ms, System: 2.9 ms]
  Range (min … max):    17.0 ms …  28.7 ms    3000 runs

import doctest experiments (no diff)

➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 "./python -c 'import doctest'"
Benchmark 1: ./python -c 'import doctest'
  Time (mean ± σ):      34.8 ms ±   0.3 ms    [User: 30.2 ms, System: 4.6 ms]
  Range (min … max):    34.2 ms …  35.7 ms    84 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 "./python -c 'import doctest'"
Benchmark 1: ./python -c 'import doctest'
  Time (mean ± σ):      35.6 ms ±   0.5 ms    [User: 30.8 ms, System: 4.8 ms]
  Range (min … max):    34.9 ms …  37.9 ms    81 runs

import logging experiments (no diff)

➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 --runs 2000 "./python -c 'import logging'"
Benchmark 1: ./python -c 'import logging'
  Time (mean ± σ):      20.9 ms ±   0.7 ms    [User: 17.7 ms, System: 3.1 ms]
  Range (min … max):    20.1 ms …  32.7 ms    2000 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 --runs 2000 "./python -c 'import logging'"
Benchmark 1: ./python -c 'import logging'
  Time (mean ± σ):      20.7 ms ±   0.5 ms    [User: 17.7 ms, System: 3.0 ms]
  Range (min … max):    20.0 ms …  30.8 ms    2000 runs

import pdb experiments (no diff)

➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 --runs 2000 "./python -c 'import pdb'"
Benchmark 1: ./python -c 'import pdb'
  Time (mean ± σ):      29.3 ms ±   0.9 ms    [User: 25.0 ms, System: 4.2 ms]
  Range (min … max):    28.2 ms …  37.9 ms    2000 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 --runs 2000 "./python -c 'import pdb'"
Benchmark 1: ./python -c 'import pdb'
  Time (mean ± σ):      30.1 ms ±   1.3 ms    [User: 25.9 ms, System: 4.2 ms]
  Range (min … max):    28.8 ms …  44.2 ms    2000 runs

import py_compile experiments

➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 --runs 2000 "./python -c 'import py_compile'"
Benchmark 1: ./python -c 'import py_compile'
  Time (mean ± σ):      11.7 ms ±   0.5 ms    [User: 9.6 ms, System: 2.0 ms]
  Range (min … max):    10.9 ms …  19.5 ms    2000 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 "./python -c 'import py_compile'"
Benchmark 1: ./python -c 'import py_compile'
  Time (mean ± σ):      18.2 ms ±   0.5 ms    [User: 15.4 ms, System: 2.7 ms]
  Range (min … max):    17.4 ms …  21.0 ms    159 runs

import pydoc experiments

➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 "./python -c 'import pydoc'"
Benchmark 1: ./python -c 'import pydoc'
  Time (mean ± σ):      32.6 ms ±   0.4 ms    [User: 28.4 ms, System: 4.2 ms]
  Range (min … max):    31.8 ms …  34.3 ms    87 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 "./python -c 'import pydoc'"
Benchmark 1: ./python -c 'import pydoc'
  Time (mean ± σ):      34.3 ms ±   0.3 ms    [User: 30.2 ms, System: 4.1 ms]
  Range (min … max):    33.5 ms …  35.2 ms    84 runs

import unittest experiments

➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 "./python -c 'import unittest'"
Benchmark 1: ./python -c 'import unittest'
  Time (mean ± σ):      21.9 ms ±   0.3 ms    [User: 18.4 ms, System: 3.4 ms]
  Range (min … max):    21.3 ms …  22.8 ms    133 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 "./python -c 'import unittest'"
Benchmark 1: ./python -c 'import unittest'
  Time (mean ± σ):      23.3 ms ±   0.3 ms    [User: 19.5 ms, System: 3.7 ms]
  Range (min … max):    22.6 ms …  24.3 ms    123 runs

import xmlrpc experiments (no diff)

➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 --runs 3000 "./python -c 'import xmlrpc'"
Benchmark 1: ./python -c 'import xmlrpc'
  Time (mean ± σ):       9.1 ms ±   0.4 ms    [User: 7.3 ms, System: 1.8 ms]
  Range (min … max):     8.7 ms …  14.6 ms    3000 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 --runs 3000 "./python -c 'import xmlrpc'"
Benchmark 1: ./python -c 'import xmlrpc'
  Time (mean ± σ):       9.1 ms ±   0.4 ms    [User: 7.4 ms, System: 1.7 ms]
  Range (min … max):     8.6 ms …  19.6 ms    3000 runs
➜  cpython git:(lazy-imports-traceback) ✗ hyperfine --warmup 11 "./python -c 'import xmlrpc'"
Benchmark 1: ./python -c 'import xmlrpc'
  Time (mean ± σ):       8.8 ms ±   0.6 ms    [User: 7.3 ms, System: 1.5 ms]
  Range (min … max):     8.3 ms …  14.5 ms    277 runs
➜  cpython git:(3d3a4beefe) ✗ hyperfine --warmup 11 "./python -c 'import xmlrpc'"
Benchmark 1: ./python -c 'import xmlrpc'
  Time (mean ± σ):       8.7 ms ±   0.2 ms    [User: 7.4 ms, System: 1.4 ms]
  Range (min … max):     8.2 ms …   9.8 ms    303 runs

• Issue: Improve import time of various stdlib modules #118761

[picnixz]

traceback is generally used in conjunction with other debugging modules, so I'm not sure it's worth the change. I'd like to mention that I also benchmark the import times using -X importtime as they don't suffer from startup time. Now, if we don't see improvements overall, I don't think we should actually do the change. I only changed modules for which import time is reduced by at least 20% (using -X importtime) or where we gain something noticeable on hyperfine. Most of your results show <10% improvements or no changes at all, so I don't think we need to do this. We definitely don't want to make all imports as lazy IMO.

[AA-Turner]

Please see my comment in your other PR, and also Benedikt's above.

A

[donBarbos]

Ok, i realized that this PR was a mistake and i will improve import time of each module separately. Maybe i will send PR for same module but without some other imports