Property

Definition

Context switches

The rate of switches from one thread to another, per second. 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. Windows NT uses process boundaries for subsystem protection, in addition to user and privileged modes. Thus some work done by Windows NT on behalf of an application appears in other subsystem processes in addition to the privileged time in the application. Switching to the subsystem causes one context switch in the application thread. Switching back causes another context switch in the subsystem thread.

CPU queue length

Number of threads in the processor queue. There is a single queue for processor time even on computers with multiple processors. Unlike disk counters, this property counts ready threads only, not threads that are running. A sustained processor queue of greater than two threads generally indicates processor congestion. This property displays the last observed value only; it is not an average.

System calls

Combined rate of calls to Windows NT system server routines by all processes running on compute, per second. These routines perform all of the basic scheduling and synchronization of activities on the computer, and provide access to non- graphic devices, memory management, and name space management. This property displays the difference between the values observed in the last two samples, divided by the duration of the sample interval.