iOS 15 Simulator uses 2-4x more memory than iOS 14 Simulator

Number:rdar://FB9722379 Date Originated:Oct 25, 2021
Status:Open Resolved:
Product:Simulator Product Version:Xcode 13
Classification: Reproducible:
Please describe the issue:
I noticed that development in Xcode 13 is noticeably slower than in previous Xcode versions. I started digging in and noticed that memory use of iOS 15 Simulator is few times larger than for iOS 14.

Please list the steps you took to reproduce the issue:
1. Open Xcode 13 or 13.1 RC on macOS Big Sur 11.6.
2. Open Devices and Simulators window in Xcode and make sure you have at least two simulators created with iOS 14 and 15, e.g. iPhone 8 with iOS 15 and iPhone 8 with iOS 14.5.
3. Right click on Xcode's icon in the dock, select Open Developer Tools and then Simulator.
4. Right click on Simulator's icon in Dock, select Device, then iOS 14.5 and finally iOS 8 14.5. Make sure you have only that one device running.
5. Open a tool that shows memory use of a process including all its children (I used but the same can be done in Activity Monitor (by viewing All Processes, Hierarchically) and searching for Simulator or launchd_sim. Notice that iOS 14.5 Simulator processes uses about ~1-2GB of memory.
6. Now close iOS 14.5 Simulator and open iOS 15 Simulator. Make sure you have only that one device running.
7. Repeat step 5, you'll notice that this simulator takes a lot more memory, on my system between 4 and 6 GB.

I'm attaching a CSV file with full list of processes ran by each Simulator version but here's memory use comparison for a few processes:

Process name | iOS 15 (in MB) | iOS 14 (in MB)
AccountExtension | 42.9 | 2.2
ScreenTimeAgent | 79.2 | 4.8
SpringBoard | 191.2 | 51.4
suggestd | 48.2 | 8.4

What did you expect to happen?
I didn't expect such significant memory requirement increase in iOS 15 Simulator compared to iOS 14.5.

What actually happened?
iOS 15 Simulator uses seemingly too much memory just idling. You need ~10GB just to run one Simulator and SwiftUI preview. I'd like to know if this is expected behavior (in that case please let us know what caused such a vast increase - e.g. through Xcode's release notes) or a regression.


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