@Linchin

Using pytest-xdist for tests that run under pytest shortens the time for a number of our CI/CD checks. In this image, darker green means more time savings. For some checks we cut total time by five minutes.

Our two worst offenders do not benefit, because:

• PRESUBMIT: has nox sessions internally and though each is less than 2 minutes long, each goes through a virtualenv setup, package install, etc and does so sequentially thus by the time we finish ~10 sessions, we have aggregated 13 minutes). This should be broken into individual CI/CD checks (out of scope).
• LINTING-TYPING: does not use pytest, instead these tests run using mypy, pytype, etc. pytype is the long pole in tent at 10 minutes. Despite this, these should be broken into individual CI/CD checks to allow more of them to run in parallel (out of scope). It may be possible to provide a wrapper to run pytype against multiple files in parallel using multiprocessing or subprocess modules (out of scope).