On a UNIX based system (e.g. Linux), why the user interface or the system itself can slow down by an incredible amount even if the CPU usage is below 10% and there is no disk activity?
Could it be a bug in the operating system?
Note: this question is general on purpose, i.e. not related to any specific case. It is intended to know if it is normal for an OS to be unresponsive even if its resources are available. For the same question related to a specific case, see this link.