Not a memory leak. Additional memory is allocated for TemporalAA render targets and the increase is due to the way in which the RTs are managed when toggling PIE. Memory shouldn't increase over time.
There appears to be a memory leak when you PIE and then exit PIE.
Users are reporting that each time they PIE, their RAM usage jumps up, say, 10MB, then when you exit PIE, it only drops down 5MB. So if you repeatedly PIE during one session, the editor keeps increasing in memory usage.
I used Content Examples for my repro, but I also reproduced with the Answerhub user's project:
Users claim this didn't occur in 4.6.1, testing for a regression right now
1. Launch Content Examples
2. Open Math Hall map (515MB)
3. PIE and run down the map (803MB) (first PIE is always a bigger jump than the rest)
4. Exit PIE (800MB)
5. Wait about 30 seconds
6. PIE and run down the map (805MB)
7. Exit PIE (801MB)
8. PIE (806MB)
9. Exit (803MB)
10. PIE (810MB)
11. Exit (806MB)
Results: Editor doesn't takes up memory, but doesn't dump all of it when you exit PIE. I only chose Math Hall because it takes up a lot of resources.
Head over to the existingAnswerHub thread and let us know what's up.