This screenshot tells all:
Yes, I invalidated caches and restarted. No matter what I do, this process balloons to almost 7GB of memory usage. It's been getting worse and now it's affecting my job. I submitted this same issue on this page https://www.jetbrains.com/help/rider/Cleaning_System_Cache.html but my comments were deleted and I was not contacted by JetBrains.
Please don't make me go back to Visual Studio. Please.