FWIW Mac jobs are also often capacity-limited on Mozilla infrastructure. It's not unusual to have thousands of jobs waiting on hundreds of machines, which leads

FWIW Mac jobs are also often capacity-limited on Mozilla infrastructure. It's not unusual to have thousands of jobs waiting on hundreds of machines, which leads to multi-hour queues at peak times. Fundamentally the problem with CI testing on Mac is that Apple don't provide the components you want to build a large pool of machines at reasonable cost, so everyone ends up doing slightly mad things involving hundreds of mac minis (obviously the Windows situation also isn't great; this kind of infrastructure loves free software on commodity hardware).