My server's been exhibiting some very strange behavior lately. Every couple of days I run into a situation where one core (core #0) on the quad core CPU starts continuously using around 34% of CPU, but I'm not able to see (using htop) any process that's responsible for using all that CPU. Even when I tell htop to show me kernel threads too, I still am not able to see the offending process. Every process remains under 1% CPU usage (except for occasional, small, short-lived spikes up) yet the CPU usage on that core remains permanently hovering at around 34%. The problem goes away when I reboot, but then comes back with a day or so. I'm rather stumped as to how to fix this. The server is a bit old, running an up-to-date installation of Arch on a Intel Core 2 Quad Q6600 CPU. Any suggestions anyone might have as to either what might be going on here, or how to go about debugging it would be greatly appreciated. Thanks! DR