What does com.apple.CoreSimulator.CoreSimulatorService do?

Question

Our iOS automation tests on simulator have gone through disaster since upgrading to Xcode6. We can observe view switching slowing down, UIAutomation felt it too and often returned an empty or not fully updated app main window, you can imagine the stability.

Part of the reason is that we have slow VMs, but still we need to find ways to workaround it.

Then I notice there's the CoreSimulatorService process staying alive between the launches and shutdowns of simulator. So I killed it to see what change would it make:

killall -9 com.apple.CoreSimulator.CoreSimulatorService

After it was killed and relaunched, the performance of simulator seem to get much better, at least I don't see random fails anymore (hopefully). I guess this is kind of cleaning up.

So I hope to get a better idea about what function does CoreSimulatorService perform exactly?

Also, I am confused about where to find the documents when Apple releases new things (forgive my ignorance). For example, I didn't find any documents in iOS developer library mentioning simctl except Xcode Release Note.

Thanks!