Significant performance regression with coverage==4.4

Issue #579 resolved
Jacopo Notarstefano created an issue

Hi, we're experiencing a significant performance regression in our test suite when using pytest-cov==2.4.0 and coverage==4.4.

In fact, one of our builds times out with this version (, but works just fine with the previous coverage==4.4b1 (

I didn't research further what could be causing this bug, but I wanted to give you a heads up that something might be wrong, either here or in the interaction with pytest-cov.

Comments (6)

  1. Ned Batchelder repo owner

    There was a problem earlier with bad linux wheels, which meant you could have been using the Python tracer instead of the C tracer. This would significantly slow down the test run. I thought I had removed the bad wheels before that linked build was run, but maybe there's caching? Try using 4.4 again, and we can look to see if it's installed from a wheel or not.

  2. Akihiro Motoki

    Could you release a new version like 4.4.1 for this fix? Even though it is a packaging problem, it is recommended to use a new version. Otherwise, if users cache or mirror a python package, they cannot recognize the replaced version.

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