3.2.2.2. The Operating System

It is difficult to determine how much processing power is consumed by the operating system. The reason for this is that operating systems use a mixture of process-level and system-level code to perform their work. While, for example, it is easy to use a process monitor to determine what the process running a daemon or service is doing, it is not so easy to determine how much processing power is being consumed by system-level I/O-related processing (which is normally done within the context of the process requesting the I/O.)
In general, it is possible to divide this kind of operating system overhead into two types:
  • Operating system housekeeping
  • Process-related activities
Operating system housekeeping includes activities such as process scheduling and memory management, while process-related activities include any processes that support the operating system itself, such as processes handling system-wide event logging or I/O cache flushing.