Recently I have experienced, that Xcode's simulator has become extremely slow. Also if I create a new app and run it i, the transition between the launch screen and the first view controller takes about 3 seconds. Luckily it is only the iOS 9 simulator and not iOS 8 or lower. I have upgraded to Xcode 6.4 and I also have Xcode 7.0 beta 3 installed. Has anyone experienced the same? I have tried to uninstall both Xcode versions, but it didn't help.
If you press command+T it triggers the 'Slow animations' feature. I didn't noticed this setting until now. Doh!
In Simulator menu, go to Debug > Slow Animations , and uncheck this option or simply do:
⌘ + T
XCODE 9 BUG. This is officially confirmed to be an issue with Xcode 9.0 and its iOS 11 simulator — it affects any OpenGL-using application.
See: https://github.com/mapbox/mapbox-gl-native/issues/9959
Also: https://twitter.com/xenadu02/status/911463433521860609
:( Hope this helps.
Currently only iOS11 simulator is slow.
You can download additional iOS10 simulator which works perfectly.
Choose Xcode -> Product -> Destination -> Download simulators... Then select any iOS10 simulator from the list (e.g. 10.3.1).
After that you will choose iOS version for most devices:
This has been fixed in Xcode 9.1 beta 2
Fixed an issue in Simulator’s OpenGL that could cause SceneKit apps to run slowly and the CPU to hit 100% when attempting to pan in an MKMapView.
It's known bug by apple developer see below link https://forums.developer.apple.com/thread/83570
I had this same problem, and after scratching my head for a while, I realized that having the Xcode "Organizer" window open while running the Simulator causes it to behave very slowly. So for anyone who doesn't have the "slow animations" option ticked, check that the Organizer window isn't open.
I believe this is an issue with El Capitan, not necessarily Xcode 7 or iOS 9. https://developer.apple.com/library/prerelease/ios/releasenotes/General/RN-iOSSDK-9.0/index.html
来源：https://stackoverflow.com/questions/31378232/xcode-simulator-animations-extremely-slow-when-played-in-editor