If your System Administrator (or you) can't identify the problem, and if a reboot doesn't resolve it, I wouldn't wait for Thwack folks to get back to you with an answer or their experiences, I'd call Solarwinds Tech Support and get a case started.
That way someone's working on it for you immediately, while the Thwack group may take a day or a month to get back to you with their experiences.
For example, I've not upgraded to 12.1 yet, preferring to see how others' experiences go. You're a perfect case in point, and I'll be watching this thread to learn what you discover is running your CPU so high. Here's hoping others have your answer, or at least will report their 12.1 CPU utilization for your comparison.
We have a similar issue.
Used physical memory is at 96%.
Solarwinds.InformationService.ServiceV3.exe process consuming around 4-4.5GB.
Solarwinds.Collector.Service.exe process consuming around 2GB.
Version: NPM 188.8.131.520
Windows Server 2008 R2
12.0 GB RAM
We are unable to access the web service during this period of high utilization - Unexpected Website Error: Request timed out.
Unfortunately, I don't have a pre-184.108.40.2060 memory baseline.
Can you tray reinstall this services.
I upgraded to 12.1 last week.... my memory utilization is more or less static. (64-65%)
16 GB RAM
HOST = ESXi V 6.0