test_ok2/bench/xunit.py

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python: fix quadratic behavior in collection of items using xunit fixtures Since commit 0f918b1a9dd14a2d046 pytest uses auto-generated autouse pytest fixtures for the xunit fixtures {setup,teardown}_{module,class,method,function}. All of these fixtures were given the same name. Unfortunately, pytest fixture lookup for a name works by grabbing all of the fixtures globally declared with a name and filtering to only those which match the specific node. So each xunit-using item iterates over a list (of fixturedefs) of a size of all previous same-xunit-using items, i.e. quadratic. Fixing this properly to use a better data structure is likely to take some effort, but we can avoid the immediate problem by just using a different name for each item's autouse fixture, so it only matches itself. A benchmark is added to demonstrate the issue. It is still way too slow after the fix and possibly still quadratic, but for a different reason which is another matter. Running --collect-only, before (snipped): 202533232 function calls (201902604 primitive calls) in 86.379 seconds ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 85.688 85.688 main.py:320(pytest_collection) 1 0.000 0.000 85.688 85.688 main.py:567(perform_collect) 80557/556 0.021 0.000 85.050 0.153 {method 'extend' of 'list' objects} 85001/15001 0.166 0.000 85.045 0.006 main.py:785(genitems) 10002 0.050 0.000 84.219 0.008 runner.py:455(collect_one_node) 10002 0.049 0.000 83.763 0.008 runner.py:340(pytest_make_collect_report) 10002 0.079 0.000 83.668 0.008 runner.py:298(from_call) 10002 0.019 0.000 83.541 0.008 runner.py:341(<lambda>) 5001 0.184 0.000 81.922 0.016 python.py:412(collect) 5000 0.020 0.000 81.072 0.016 python.py:842(collect) 30003 0.118 0.000 78.478 0.003 python.py:218(pytest_pycollect_makeitem) 30000 0.190 0.000 77.957 0.003 python.py:450(_genfunctions) 40001 0.081 0.000 76.664 0.002 nodes.py:183(from_parent) 30000 0.087 0.000 76.629 0.003 python.py:1595(from_parent) 40002 0.092 0.000 76.583 0.002 nodes.py:102(_create) 30000 0.305 0.000 76.404 0.003 python.py:1533(__init__) 15000 0.132 0.000 74.765 0.005 fixtures.py:1439(getfixtureinfo) 15000 0.165 0.000 73.664 0.005 fixtures.py:1492(getfixtureclosure) 15000 0.044 0.000 57.584 0.004 fixtures.py:1653(getfixturedefs) 30000 18.840 0.001 57.540 0.002 fixtures.py:1668(_matchfactories) 37507500 31.352 0.000 38.700 0.000 nodes.py:76(ischildnode) 15000 10.464 0.001 15.806 0.001 fixtures.py:1479(_getautousenames) 112930587/112910019 7.333 0.000 7.339 0.000 {built-in method builtins.len} After: 51890333 function calls (51259706 primitive calls) in 27.306 seconds ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 26.783 26.783 main.py:320(pytest_collection) 1 0.000 0.000 26.783 26.783 main.py:567(perform_collect) 80557/556 0.020 0.000 26.108 0.047 {method 'extend' of 'list' objects} 85001/15001 0.151 0.000 26.103 0.002 main.py:785(genitems) 10002 0.047 0.000 25.324 0.003 runner.py:455(collect_one_node) 10002 0.045 0.000 24.888 0.002 runner.py:340(pytest_make_collect_report) 10002 0.069 0.000 24.805 0.002 runner.py:298(from_call) 10002 0.017 0.000 24.690 0.002 runner.py:341(<lambda>) 5001 0.168 0.000 23.150 0.005 python.py:412(collect) 5000 0.019 0.000 22.223 0.004 python.py:858(collect) 30003 0.101 0.000 19.818 0.001 python.py:218(pytest_pycollect_makeitem) 30000 0.161 0.000 19.368 0.001 python.py:450(_genfunctions) 30000 0.302 0.000 18.236 0.001 python.py:1611(from_parent) 40001 0.084 0.000 18.051 0.000 nodes.py:183(from_parent) 40002 0.116 0.000 17.967 0.000 nodes.py:102(_create) 30000 0.308 0.000 17.770 0.001 python.py:1549(__init__) 15000 0.117 0.000 16.111 0.001 fixtures.py:1439(getfixtureinfo) 15000 0.134 0.000 15.135 0.001 fixtures.py:1492(getfixtureclosure) 15000 9.320 0.001 14.738 0.001 fixtures.py:1479(_getautousenames)
2020-10-23 23:51:51 +08:00
for i in range(5000):
exec(
f"""
class Test{i}:
@classmethod
def setup_class(cls): pass
def test_1(self): pass
def test_2(self): pass
def test_3(self): pass
"""
)