High System Interrupts

I just finished fixing a problem with one of my VMs using hardware pass-through. It was one of the machines getting the second USB controller. When I went into the OS (Windows), it was very slow. When checking task manager, it showed the first CPU floating around 30% and the second CPU was at idle. When looking at the processes, there wasn't anything consuming CPU cycles. Then, I saw that it was hardware system interrupts within the Resource Monitor.

I isolated it to the USB controller vice the video card by removing both and adding them back one at a time. I tried a couple different scenarios with switching the controller to other VMs and whatnot, but with no luck.

To resolve the problem, I de-selected all the hardware for pass-through, rebooted, reconfigured the pass-through and rebooted a second time. I checked my VMs to ensure they were still configured with the correct hardware items and powered everything back on. I think it might have happened when I was adding additional hardware for pass-through and it just got out of sync somewhere.

Within Linux, I'm fairly certain you can use iostat to track down culprits with high system interrupts. I think it was the tool I used a few years ago to track down something (it was either the analog phone card or a dying hard drive from what I can remember).