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use parallel front end(-Zthreads=2) in ui tests #129799
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rustbot has assigned @Mark-Simulacrum. Use |
Some changes occurred in src/tools/compiletest cc @jieyouxu |
Due to the nature of parallel compiler bugs not being reliably reproducible most of the time, I don't think we will ever be able to turn this on in ci permanently, as a default at least. What will happen is that we run into weird one-in-50 edge cases where tests fail or ICEs happen on seemingly unrelated PRs or random targets, while the pr that introduced the bug passed in ci by pure luck. |
Makes sense. The biggest value of this PR may be to find bugs caused by parallel front end through UI testing. We found a deadlock bug in |
We could add a special CI job that enables more threads, as a sort of a fuzzer, and allow it to fail (or just run it on a different rustc fork, for example). |
You should check the walltime impact of running UI tests locally. They don't run under a jobserver, so it'll likely end up oversubscribing the CPU cores. OTOH UI tests are tiny, so I wonder how much of a chance it even gets at running multiple threads. |
There are merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged. You can start a rebase with the following commands:
The following commits are merge commits: |
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The job Click to see the possible cause of the failure (guessed by this bot)
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☔ The latest upstream changes (presumably #130179) made this pull request unmergeable. Please resolve the merge conflicts. |
The main value of this PR draft is to find potential bugs, which has been completed and this PR is closed. |
use parallel front end(-Zthreads=2) in ui tests
Test the functionality of the parallel frontend to support stabilization