cabal-testsuite takes ages to run on Windows and GHC-8.8 or GHC-8.10

[phadej]

I have no clue what might be a reason. See recent master CI runs.

[phadej]

Comparison, on GitHub Actions. Faster is GHC-8.6.5, slower GHC-8.10.2 (8.10.2.2 from chocolatey):

cabal-testsuite\PackageTests\NewBuild\T4450\cabal.test.hs                                                                         OK (59.93s)
cabal-testsuite\PackageTests\NewBuild\T4450\cabal.test.hs                                                                         OK (11.99s)

On AppVeyor

cabal-testsuite\PackageTests\NewBuild\T4450\cabal.test.hs                                                                         OK (73.75s)
cabal-testsuite\PackageTests\NewBuild\T4450\cabal.test.hs                                                                         OK (14.84s)

Other individual tests seem to have similar-ish slowdown (the T4450 is just one of the slowest ones).

[jneira]

This continue being a problem, see https://github.com/haskell/cabal/actions/runs/1965714393 for example

• 8.6.5: 22 m
• 8.10.4: 53 m

[jasagredo]

Is this still relevant? Those GHCs are considered old now

[geekosaur]

It is certainly still true on the Windows part of CI.

[jasagredo]

Im not sure there is anything we can do here to speed it up. It is also true for MacOS.

[ulysses4ever]

MacOS is even worse. Not sure how we could act on this. If I were to speculate, I'd say it's a GHC issue. Although, Matthew recently discovered a massive slowdown on Windows due to how slow skipping tests is.

[ulysses4ever]

#9426