Either the memory isn't completely cleared or it gets fragmented. Having done multiple successive renders of my "4.7 trillion triangle" scene on an 8GB machine, with the memory use exceeding 3GB each time, I saw memory use go down to the same level each time, without rebooting. I was able to render fine multiple times, without restarting. I suspect however that if I had only had 4GB of memory it wouldn't have worked, perhaps due to memory fragmentation. I think the actual memory in use was not the issue. But I can't be sure.
We do of course try to keep on top of reproducible memory leaks and errors, but we have not seen anything significant of that kind since the release of 2.0.3.1. One way to test the "fragmentation" theory is whether restarting *just* TG2 fixes it. If so, then it's probably a TG2 issue of some kind (although not necessarily unreleased memory). If you have to restart your whole system, then it's more likely system-related, possibly memory fragmentation.
- Oshyan