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When using "-n auto", count the number of physical CPU cores instead of logical ones

See original GitHub issue

I have a laptop with 6 physical CPU cores and hyper-threading. The code from auto_detect_cpus gives 12:

from os import sched_getaffinity
len(sched_getaffinity(0))
Out[24]: 12

The optimal number of parallel processes though is 6. Tests run slower when using 12 processes. Did you consider using psutil.cpu_count(logical=False)?

Issue Analytics

State:
Created 3 years ago
Reactions:5
Comments:7 (5 by maintainers)

Top GitHub Comments

1reaction

AdrienPensartcommented, Aug 18, 2020

Guys you changed something important there, now, how can we specify $(nproc) in pytest.ini or pyproject.toml ? If -n auto does not work anymore, the tests are not adapted when ran on different kind of machines 😕 If tests are IO-bounded, and not CPU-bounded, it drastically ruin testing time.

maybe a better option like “-n [auto|ncpus|ncores|{n}]” could be nice ?

0reactions

nicoddemuscommented, Aug 19, 2020

Hi @AdrienPensart,

If -n auto does not work anymore, the tests are not adapted when ran on different kind of machines 😕

-n auto should still be working… can you open an issue if it is not working for you?

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