Severe performance problems with Xcode 15

Hello folks!

The macOS Infra team at CircleCI has been investigating the reports of poor performance when using Apple’s iOS simulators in the virtualized macOS environment. Thus far we haven’t been able to identify any viable workarounds. We will continue to experiment with the environment and if we identify any potential solutions, we’ll share our findings.

As noted in the thread above, the Xcode 15 release notes indicate a couple of known issues with Xcode 15 and the simulators:

  1. Executing Unit/UI tests from Xcode on the iOS Simulator takes an extended time to launch on first run of the suite. (115187363) (110330776) (FB12237092)
  2. The simulator may crash when opening Settings or Action Button settings on iPhone 15 Pro devices. (115388496)

Also, please keep in mind that the Apple Silicon executors are a virtualized environment, and aren’t running on bare metal Apple Silicon. This virtualization technology (the Apple Virtualization Framework) may ultimately be the root cause of the problems we’re seeing here with the simulators, in which case we encourage everyone to submit bug reports to Apple regarding simulator startup and runtime issues.