Windows Tools

Pfmon.exe: Page Fault Monitor

Overview | Notes | Syntax | Examples | Related Tools Open Command Prompt

This command-line tool allows a developer or system administrator to monitor page faults that occur while an application is running. PFMon is especially useful to trace hard page faults. (You can easily resolve soft page faults with Virtual Memory Manager.) A sustained high rate of hard page faults might indicate a shortage of memory and can cause a disk bottleneck. Use PFMon to trace the source and number of page faults in a process and display the data in the command window, write it to a log file, or both.


Notes

Corresponding UI

There is no corresponding user interface for PFMon.

Concepts

A page is a fixed amount of data. When you run a program, the microprocessor stores pages of data that it predicts you will need in main memory, also known as RAM. Pages of data that are not needed are left on your storage device, such as your hard disk.

A page fault occurs when a process refers to a virtual memory page that is not in the working set (the physical memory visible to the program) in main memory.

There are two kinds of page faults: soft and hard. A soft page fault occurs when a process refers to a virtual memory page that is not in the working set, but does not require that the page be retrieved from disk. This can happen when the page is on the standby list in main memory or when the page is being shared with another process. A hard page fault occurs when a virtual memory page is not found in main memory and must therefore be retrieved from disk.

Neither type of page fault is an error.

Hard page faults indicate that your program is reading from and writing to disk. A rise in the number hard page faults generated by a specific program increases the possibility of a disk bottleneck. PFMon helps you determine the number, type, and source of soft and hard page faults that your application generates.

System Requirements

The following are the system requirements for PFMon:

Files Required