Performance issue on Porter

[MTCam]

CI has been taking a really long time on Porter since Wednesday.
Started here: (https://github.com/illinois-ceesd/mirgecom/actions/runs/3842730601/jobs/6544320897)
Today's run: (https://github.com/illinois-ceesd/mirgecom/actions/runs/3851480094/jobs/6562700607)

The performance drag is persistent across branches, and appears to be affecting all branches:
(https://github.com/illinois-ceesd/mirgecom/actions/runs/3851378596/jobs/6562480056)

Issue appears to be only in CI. Have been unable to reproduce by hand on Porter so far.

[inducer]

It might be good to use per-run caches and make sure those are empty before each run.

[MTCam]

It might be good to use per-run caches and make sure those are empty before each run.
👍

Spot on. Your deletion of the cache directories on Porter appears to have cleared up the problem.
(https://github.com/illinois-ceesd/mirgecom/actions/runs/3851480094/workflow)