Performance Monitor Collects Data for Only One Instance

• Microsoft Windows NT operating system, version 3.1
• Microsoft Windows NT Advanced Server, version 3.1

To display Performance Monitor statistics, such as % Processor Time, for two instances of the same program, you must copy the program to another name on your hard disk.

For example, consider a program called TESTDEMO.EXE that calls various GDI functions based on a menu selection. To chart the performance of two different instances of the application simultaneously to see how the different functions use the processor, make a copy of the program with a different name (for example, TESTDEM1.EXE).

If the program is a 16-bit Windows-based application, Windows NT does not support profiling more than one copy simultaneously. Only one instance of the NTVDM exists at any one time. Windows NT cooperatively multitasks all 16-bit Windows-based applications in the NTVDM and they all appear to the Win32 Subsystem as one process. Because the Performance Monitor is a Win32 application, it only sees the one NTVDM process and it cannot separate the performance of the individual 16-bit Windows-based applications.

This behavior is necessary because process identifier values are quickly reused. If a process ID was chosen as a unique value and the process died, another program might use that process ID almost immediately.

For example, consider a process with Process ID 112. If you chart the performance of this process, stop the process and restart it, it may restart with a different process number and the Performance Monitor would not display it.

To view statistics for two processes simultaneously, give each process a unique name. Then the Performance Monitor can provide statistics for each process no matter how many times the process starts and stops.