Linux – cpu utilization over 100% in linux system

In cases like this, you need to go beyond task manager and looking at % CPU usage. That does not tell you if something is adversely affecting performance. For a case like this, the next step would be to use Performance Monitor to view System\Processor Queue Length. This tells you if processes are waiting for the CPU to become idle possibly affecting performance. This is similar to what you see in the top or load commands in Unix.

This article has a good description of the performance metrics to look at when troubleshooting these issues. It was originally for NT4, but still applies to newer versions.

Here is a more recent article from the Windows Performance Team talking about how to hunt down performance issues with the CPU.

What about SQL Server maintenance and backup plans? Maybe some are executing at night, and they have strong chances to fill all the resources available.

Windows defragmentation is another process which can take a large amount of CPU power. See defrag logs to figure out the last date it was running.