Measuring the Change

These architectural changes are manifest in several different ways but are most evident when you monitor the behavior of graphics-intensive applications.

The following figure is a graph of a Windows NT 3.0 running GDIDemo, a graphics demonstration tool in the Win32 Software Development Kit. All features of the tool were used simultaneously to generate the most graphics activity.

In this example, the processor is 100% busy and is spending most of its time running Csrss.exe. The following figure shows the same program running on Windows NT 4.0.

There are significant differences between the performance evidenced in the graphs.

Processor Time:

• The Windows NT 3.51 graph shows that the GDIDemo test used 100% of processor time. (System: % Total Processor Time is the thick, black line is running along the top of the graph).

• The Windows NT 4.0 graph shows that the GDIDemo test used an average of 50% of processor time. . (System: % Total Processor Time is the gray line)

Some of this might be attributable to the new architecture, but it probably results from improvement in processor technology. The Windows NT 3.51 graph was captured on a computer with a 386 processor; the Windows NT 4.0 was captured on a computer with a 486 processor.

Process Time:

• In the Windows NT 3.51 graph, Process: % Processor Time for GDIDemo (the thin, black line) runs between 10 and 20% while Process: % Processor Time for CSRSS (the white line) averages between 75% and 85%. This indicates that in order to run GDIDemo, the processor was spending 10–20% of its time running in GDIDemo code and the remainder running in CSRSS code on behalf of GDIDemo.

• In the Windows NT 4.0 graph, Process: % Processor Time for GDIDemo (the thin, black line) runs between 25 and 35% while Process: % Processor Time for CSRSS (the white line) runs at nearly 0%. The processor may have been running some system code on behalf of GDIDemo, but it was not in CSRSS.

The following graph of the Windows NT 4.0 test is the same as the previous one, but includes counters for privileged and user time and interrupts.

From top to bottom, the lines represent:

• System: % Total Processor Time

• System: % Total Privileged Time

• Process: % Processor Time: GDIDemo

• System: % Total DPC Time

• System: % Total User Time

• System: % Total Interrupt Time

• Process: % Processor Time: CSRSS

This data demonstrates that in Windows NT 4.0, GDIDemo graphics processing time is spent running in privileged mode code in the Windows NT Executive. In previous versions of Windows NT, graphics processing was part of CSRSS and ran mainly in user mode.