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From 2022.1 onwards all undo actions involving a prefab instance ensures a prefab merge is always made in order to detect issues and fix them during undo. This does unfortunately have the side effect of slowing down some undo actions compared to previous versions where prefabs are involved but this is expected with this stabilising change.
Reproduction steps:
1. Open the attached "repro_IN-47328.zip" project
2. Open the "SampleScene" Scene
3. Open the Profiler tab
4. Open the Profile Analyzer tab
5. Select Edit Mode in the Profiler tab
6. Set Frame Count to 2000 frames in Profiler Preferences (Edit > Preferences > Analysis > Profiler)
7. Enter the Play Mode
8. Press on the Record button in the Profiler tab
9. Delete all GameObjects in the Hierarchy ("Ctrl + A > Del" key combination), then Undo ("Ctrl + Z" key combination)
10. Press the record button again to stop profiling
11. Go to Profile Analyzer and press the "Pull Data" button
12. In the search bar, type "Undo" and you should find the "Menu.Undo" process
13. Check how long the process is
Expected result: The process takes around 30ms
Actual result: The process takes around 60ms
Reproduced with: 2022.1.0a6, 2022.3.7f1
Not reproduced with: 2021.3.29f1, 2022.1.0a5
Couldn't test with: 2023.1.8f1, 2023.2.0b4 - Couldn't resolve Console errors (they are related to "RTHandles", which are related to the "Core RP Library", which in the project is locked)
Reproduced on: Windows 10
Note:
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