Performance Objects and Counters

The performance data is grouped by performance object to which it is related. A performance object consists of performance counters, which are used to measure various aspects of system, application, or device performance. For example, the Processor object includes the Processor Time counter to measure the percentage of time the processor spends executing threads that are not idle and the Interrupts/sec counter to measure the number of device interrupts the processor receives.

An instance is a unique copy of a particular object type. Not all object types support multiple instances. For example, a Memory object has only one instance, because a system has one memory. However, the Processor object supports multiple instances, because a system can have one or more processors.

Most performance counters in Windows NT increment and are never cleared. Therefore, to obtain performance data, use the following steps.

• Take a snapshot of the relevant performance counters at the beginning of a time interval.
• Take a snapshot of the same performance counters at the end of the time interval.
• Find the difference between the counter values in the snapshots and apply the appropriate calculation function.

For a list of the system performance objects and performance counters, see Windows NT Performance Counters.