How to reproduce:
1. Open the attached “IN-149290” project
2. Select File → Build Profiles
3. In the Build Profiles window, enable “Development Build”
4. Build and run the project
5. Press the “Load GameObjects” button
6. Once loading finishes, press the “Trigger Asset GC” button
7. Quit the built application
8. Open the “Player.log”
9. Observe the GC logs at the end of the log
Actual result: The duration reported for the “Resources.UnloadUnusedAssets()” call is over 2.5-3x longer on the affected versions (Total: 897.031400 ms (FindLiveObjects: 176.205500 ms CreateObjectMapping: 203.222000 ms MarkObjects: 505.304600 ms DeleteObjects: 12.297900 ms)
Expected result: The duration reported for the “Resources.UnloadUnusedAssets()” call is around 350ms (Total: 334.590000 ms (FindLiveObjects: 148.752700 ms CreateObjectMapping: 55.615800 ms MarkObjects: 123.306700 ms DeleteObjects: 6.913800 ms)
Reproducible with: 6000.5.0b2, 6000.5.8f1, 6000.6.0a4
Not reproducible with: 6000.0.81f1, 6000.3.22f1, 6000.5.0b1, 6000.6.0b8, 6000.7.0a4
Fixed in: 6000.6.0a5
Reproducible on: Windows 10 (by user), Windows 11
Not reproducible on: No other environments tested
Note: The 2.5-3x slowdown was measured in a simplified, synthetic repro project, in the real-world application, users reported up to 10x slower times