Context Switches/sec is the rate of switches from one thread to another. Thread switches can occur either inside of a single ...

Context Switches/sec is the rate of switches from one thread to another.  Thread switches can occur either inside of a single process or across processes.  A thread switch can be caused either by one thread asking another for information, or by a thread being preempted by another, higher priority thread becoming ready to run.  Unlike some early operating systems, Windows NT uses process boundaries for subsystem protection in addition to the traditional protection of user and privileged modes.  These subsystem processes provide additional protection.  Therefore, some work done by Windows NT on behalf of an application  appear in other subsystem processes in addition to the privileged time in the application.  Switching to the subsystem process causes one Context Switch in the application thread.  Switching back causes another Context Switch in the subsystem thread.