perfmon

Perfmon, short for Performance Monitor, is a Windows utility used to monitor and analyze system performance. It provides real-time visualization of performance counters and can collect data for later analysis. Perfmon is accessed via perfmon.exe or through the Performance Monitor UI found in Administrative Tools. It relies on the Windows Performance Counter infrastructure, exposing metrics from the operating system and installed applications.

Counters are grouped into performance objects such as Processor, Memory, PhysicalDisk, and Network Interface. Each object exposes counters like % Processor Time, Available MBytes, Disk Read/Write Bytes/sec, and Bytes Total/sec. Users can add counters, adjust sampling intervals, and arrange multiple counters in graphs, histograms, or reports. Data Collector Sets can be created to log data over time for offline analysis. Logs can be saved in formats such as CSV, TSV, or binary .blg; alerts can trigger when a counter crosses a threshold; and baselines can be created for comparison.

Perfmon is commonly used by system administrators for troubleshooting, capacity planning, and performance benchmarking. It supports remote monitoring and can collect data from local and remote machines when proper permissions are configured. The tool interoperates with the Windows Performance Counters API and can be scripted or automated using PowerShell or WMI for more advanced scenarios.

Perfmon has its roots in the Windows NT era and remains a core component of Windows administration in modern editions. While powerful, monitoring can impose overhead, so sampling intervals and selected counters should be chosen carefully to balance detail against performance impact.