I've noticed that I have high kernel time when doing a lot of network traffic in Linux. I also noticed that 45% of my CPU is spent doing interrupts. How can I further troubleshoot this?
systemtap stuff is supposed to let you drill down into the kernel, and lately also applications, for tracing, troubleshooting, and debugging. Haven't used it myself.
High interrupt traffic for high network traffic might be due to less-than-bright network card or driver, perhaps a higer-end card gives better results. The kernel's handling of networking has also improved, perhaps updating the kernel helps.
OTOH, if 50% of CPU usage goes to interrupts, and CPU utilization is 3%, there should be nothing to worry about... review the data you have (and how you collected it, what the exact meaning of the numbers is) and think it over.
In the end, the question shouldn't be "Measuring foo gives bar", but start with "Performance is bad/unacceptable, what do I need to measure to find out where the bottleneck is, so I can remove it". If that leads to the above question, fine, but then you know where you are going.