That's why the test timeout on riscv64 is double that of other architectures:
Unfortunately in many cases, the performance difference seems a lot more than a factor of two.
Take rust-gix for example, looking at the results for testing migration tests I see 18-28m on amd64 53-59m on arm64 33-47m on armel 33-48m on armhf 1h59m-2h2m on i386 49m-1h37m on ppc64el 23m-55m on s390x on riscv64 it was timing out after over 8 hours. To unblock things I modified it to only test a single feature configuration. It then passed in 29 minuites. If we assume all feature configurations take the same time (very rough) then that suggests running the full set of tests on riscv64 would take of the order of 23 hours. Over 10 times worse than the next-slowest architecture.
So this hints at missing *versioned* dependencies.
It seems to me that britney's autopkgtest scheduler sometimes fails to pick up that stuff needs to go in together. Even though the main part of britney knows that they do. The end result of this is frequently that the fallback dependency solver gets triggered and autopkgtest tries to run the tests from testing against the package from unstable. This often results in a "crate directory not found" error. In other cases the fallback depsolver is not invoked or doesn't succeed and the testsuite fails with a "fail badpkg" error. Why this is happening I'm not entirely sure. Though I have some theories In some cases I suspect it happens because the dependencies are indirect. or even involve going down the tree and back up again. In some cases I suspect it happens because riscv64 testing is currently a basket case, so the packages are already uninstallable in testing. In some cases I suspect it happens due to the special treatment of arch all packages (rust team packages are arch any, but Jonas's packages are arch all). For example if we look at the migration page for rust-event-listener, it seems britney has done the right thing on amd64 and arm64 (where arch all packages are required to be installable) but not done the right thing on architectures where arch all packages are not required to be installable.
