Taking your system's pulse
Whether you have just installed Windows NT and want to investigate
NT further or you want to tune an existing installation, Performance Monitor
is a good place to start. This utility lets you track variations in the use
of system resources over time and set alerts on the use of specific resources. You
can even monitor systems remotely, which is a great help in tracking down
problems in your network. And Performance Monitor can measure application
performance, not just operating system performance.
You will find Performance Monitor in NT 4.0's Administrative Tools folder.
In NT 3.51 and earlier, look in the Administrative Tools program group. No major
differences in Performance Monitor's functionality exist between the versions of
NT.
Selecting Parameters to Monitor
When you first open Performance Monitor, you see the blank Chart screen. You
must select which objects, instances, and counters to monitor.
To begin, click the + icon on the toolbar, or use the Edit, Add To Chart menu
option. Screen 1 shows the result.
An object is any system component that has a set of measurable properties.
An object can be a physical component (such as a hard disk, memory, or a CPU), a
logical component (such as a disk volume), or a software component (such as a
process, a thread, or a redirector).
An instance shows how many occurrences of a particular object are in the
system. For example, Screen 1 shows only one Processor instance (in true
programming fashion, called instance 0), so you know that this computer has only
one CPU. However, if you look at the PhysicalDisk object on this computer, you
see instances 0 and 1, because you have two physical hard disks. New in NT 4.0
is Total instance, which gives you the combined values for all instances.
Each object has multiple counters, each of which is a measurable attribute
of the object. In Screen 1, the Processor object has several counters, including
the percentage of processor time in use and percentage of time the CPU spends in
Privileged and User modes. By default, Performance Monitor opens this selection
screen with the Processor object as the focus and the %Processor Time counter
highlighted. This counter is one of the most commonly used counters and,
therefore, a good choice for a default. You can monitor many counters, but some
are more important than others. Table 1 provides a good starting point for
choosing counters. Select the counters you want to monitor, and click Add to
include them in the display. For a concise and useful explanation of a counter,
click Explain. When you finish adding counters, close this selection window and
watch the graphical display.
Performance Monitor has approximately 350 different counters. Screen 2
graphs performance for several counters. The peaks in the CPU usage are from
running the Pinball utility (OK, game) in demo mode, which takes all of my
486DX4-100. At the same time, I was copying some files across the network, so I
was also measuring the disk writes and bytes per second on the network. Each
counter is a different color on the graph, and you can customize the display. If
you are showing the graph to a group of people, particularly on a projection
system, you can make the lines on the chart thicker. And if necessary, you can
vary the scale for each item, although I've found the default values are usually
close to what I want.
A legend of the monitored counters appears at the bottom of the screen.
Click a counter to have the values appear in the boxes just above the legend.
The values listed are the last, average, maximum, and minimum values, and the
timescale in seconds for the chart display.
Hints and Tips
While you're looking at the chart, press Ctrl+H. This command thickens the
white line for the counter you've selected and makes identifying this counter
easier when you have multiple counters displayed on the same screen. Press
Ctrl+H again to turn off this option.
Oh yes, let me mention a couple of things that everyone, including me,
finds confusing. First, if you want to monitor disk parameters, you have to go
to a command prompt, type
diskperf -y
and reboot the computer. To turn this option off, you must type
diskperf -n
and again, reboot. Microsoft added this step because monitoring disk
performance imposed a 1 percent to 2 percent performance penalty on a 386-based
system. Pentium and 486 systems do not suffer from this performance penalty. Now
that NT 4.0 runs only on 486 and better CPUs, Microsoft needs to consider
turning on disk monitoring as the default.
Be aware that you can easily confuse the Process and the Processor
objects. The Process object represents a running program, in other words, an
object using system resources. Its counters track how much of each system
resource the process is using. The Processor object is the CPU, which is a
system resource. Some counters, such as %Processor Time, appear in both objects,
so you have to be careful which object you select when you pick the counters.
Charts, Reports, and Logs
The chart view in Screen 2 is only one way to analyze data with Performance
Monitor. You also can generate reports and logs. A report is a
text-based view of selected counters, as shown in Screen 3, updated at
intervals. The default interval is every five seconds.
A log is a file in which you can trap data for analysis in Performance
Monitor or another utility. You can build log files on a regular schedule to see
how performance trends develop. Keep in mind that Performance Monitor does not
allow for long-term trend analysis: The best you can do is take snapshots of the
data at intervals and compare that data using a program such as Microsoft Excel.
(Some third-party programs that offer the ability to analyze trends over time
will soon be available.)
To set up the log, select the objects you want to track, as shown in Screen
4
. At this point, you select objects only, not counters. Performance Monitor
will track all the counters for each object and store them in a log file.
Next, set the Log Options. Click the Options button on the toolbar, or
select Options, Log from the menu. As Screen 5 shows, you must specify a log
filename and an update interval. You also start and stop collecting data from
this dialog box.
Once you've started data collection, the Status box you see on the upper
right side of Screen 4 changes from "Closed" to "Collecting."
After you collect the data, you can export it or look at it with Performance
Monitor. Reading the data from Performance Monitor can be confusing at first:
Use the Options, Data From menu option, and instead of measuring current
activity, read in the log file. Now if you change to the chart, alert, or report
view, you can select which counters to display (Performance Monitor limits your
choices to only those objects you monitored for the log file).
You might be wondering, "What's the point of setting an alert on the
historical data contained in the log file?" You can set an alert and see
whether the counter reached some upper or lower acceptable limit during the time
Performance Monitor was collecting the log. The alert works similarly to a
simple search function.
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