If PIE ends up loading new asset references they will not be garbage collected by the editor. Currently this is by design.
Originally, a project that uses about 500 mb of memory spikes to over 2 gigs during PIE. After exiting PIE, the memory usage remains well over 2 gigs and continues to rise.
Found in 4.10 Binary. Reproduced in 4.9.2 and Main CL 2777621.
1. Open the editor
2. Open Task Manager
3. PIE
4. Exit PIE
Result: Notice the memory spike and then remain consistent even after exiting PIE.
Head over to the existing Questions & Answers thread and let us know what's up.