PERF: Slow Windows / Ubuntu Unit Tests during Status Checks

[MartinBraquet]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this issue exists on the latest version of pandas.

• I have confirmed this issue exists on the main branch of pandas.

Reproducible Example

The Windows Unit tests are dangerously close to time out when running the checks that validate a PR.
The last unit test from a merged PR took 83 minutes, out of the 90 minutes before timeout:
https://github.com/pandas-dev/pandas/actions/runs/15019196064/job/42204122221

Furthermore, the checks in the open PR below are failing due to timeout in one of the Windows Unit tests.
https://github.com/pandas-dev/pandas/pull/61457/checks?check_run_id=42474035590
As there is only one unit test failing among all the PR checks and the Ubuntu Unit test is taking the same time in this PR as in the merged PR above, it strongly suggests that there is no issue intrinsic to the code change in the PR and that the way forward is:

• To increase the 90-min timeout in the unit test config yaml
• Or, and maybe better, to reduce the total time to run unit tests; this obviously might require a lot of work, unless some low-hanging fruits are still up for grab.

If this issue appears in all new PRs triggering the core unit tests, this requires immediate attention.

Installed Versions

Version independent

Prior Performance

No response

[MartinBraquet]

Update:
After a rerun of the checks in PR #61457, they all passed in 45 min.
This is a significant difference with the 90 min that it took for the precedent check that ran just an hour before it.
It would be interesting to determine the cause for that twofold increase in runtime.
It ran at the same time as another check from a different PR. So one hypothesis is that compute time increases if multiple checks run in parallel. If all checks share the same compute resources and each check uses most of them, then parallel runs may severely impair performance

[mroeschke]

The root issue is that creating the environment is taking significantly longer for some reason (+30 minutes) for Windows and Ubuntu (x86) environments recently. Maybe the dependency solver got updated that triggered a performance regression