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!

Shamrao

I've been exploring this service as well. One issue I think that could happen is that if you whack this service after executing something like 'xcrun simctl erase all', your simctl operation could fail, leaving you in an undesirable state for the next run. – Verdun

I don't even use XCode but com.apple.coresimulator.coresimulatorservice was taking up 97% of my CPU. Not only that, but simulatortrampoline was taking up 97% as well!? My fan was going nuts. Would like to know what caused it. – Beers

Same for me, I’m not programming at all, and yet com.Apple.CoreSimulator is showing many errors in my console (debugging the laptop not waking for hours). – Chammy

Answer 1

I just faced a unexpected CPU spike due to this process (Xcode 12 & macOS 12).

A quick look on the web showed that most of the time your look for com.apple.CoreSimulator.CoreSimulatorService you will find people afraid of "something" and that are resetting everything. Ultimately this will "resolve" (as a workaround) the problem that isn't really one.

I opened ActivityMonitor (and not just looking at iStat Menu CPU widget), I found that the process update_dyld_sim_shared_cache was responsible for this CPU high usage.

Just reading the name show that the process is probably doing something expected after all (I got this issue after an OS update).

I just waited a around half a hour and the CPU went back to normal.

Rayon