There are several types of performance counters in Windows. However, I had a hard time of understanding all these types just from their documentation. So I decided to compile some examples for each counter type.

I also wrote some C# code to demonstrate how to use performance counters. You’ll find it at the end of this article.

Notes:

• You can watch performance counters with the Performance Monitor (perfmon) that comes with Windows. However, it can’t display negative values so some counters can’t be monitored properly.
• I use the .NET names for performance counter types in this article.

• Categorization of the counter types follows the official documentation.

Terminology ∞

Performance counter

A counter to monitor performance of a running system (e.g. CPU usage). Is basically just an int.

Sampling, Measurement

Read the value of a performance counter (at a certain point in time)

Sampling rate

How often a performance counter is sampled (e.g. every second)

Time frame

Time between two samplings (usually one second)

Monotonicity

Whether you can increase and/or decrease the value of a performance counter. (Some counters require you to always increase – but not decrease – their values.)

Composite Counters ∞

Before we begin, a word about (what I call) “composite counters”.

As the name suggests, these counters are composited of two counters – a parent counter and a base counter. Parent counters can be monitored, base counters cannot.

To register (new/custom) performance counters in Windows, you need to pass a list of performance counter creation data to PerformanceCounterCategory.Create(). In this list the base counter data must come immediately after the parent counter data.

The following table lists which base counter type can be used with which parent counter type:

Base counter type	Parent (composite) counter types
AverageBase	AverageTimer32, AverageCount64
CounterMultiBase	CounterMultiTimer, CounterMultiTimerInverse, CounterMultiTimer100Ns, CounterMultiTimer100NsInverse
RawBase	RawFraction
SampleBase	SampleFraction

Instantaneous Counters ∞

Displays: the most recent measurement

Types	NumberOfItems32, NumberOfItems64, NumberOfItemsHEX32, NumberOfItemsHEX64
Description	The simplest counter; just displays the raw number without any calculations; the HEX variants indicate that the values should be displayed as hexadecimal (instead of decimal)
Example	Overall database operations
Displays as	raw count
Composite	no
Monotonicity	increasing, decreasing, remain static

 

Types	RawFraction
Description	Used to display fractions (instead of integers like with NumberOfItems); usually interpreted as percentage
Example	Percentage of maximum allowed concurrent database connections; RawFraction: current connection count; RawBase: maximum connection count
Displays as	(RawFraction / RawBase) * 100
Composite	yes (base: RawBase)
Monotonicity	increasing, decreasing, remain static

Average Counters ∞

Displays: average of values during time frame

Types	AverageCount64
Description	Used to describe how many items were processed per operation in average
Example	Database operations per transaction; for each operation, you’d increment AverageCount64 and for each completed transaction you’d increment AverageBase
Displays as	average items per operation (during the last time frame)
Composite	yes (AverageBase)
Monotonicity	increasing, decreasing, remain static

Note

The difference to RawFraction is that RawFraction would be displayed as the average since the creation/last reset of the counter, while AverageCount64 would be displayed as average during the last time frame (usually a second).

Types	AverageTimer32
Description	Used to describe how long an operation takes in average
Example	Average time each database transaction takes; for each transaction, you’d measure the execution time of the transaction with Stopwatch and increment AverageTimer32 by Stopwatch.ElapsedTicks; and for each completed transaction you’d increment AverageBase by one
Displays as	average time per operation (during the last time frame)
Composite	yes (AverageBase)
Monotonicity	increasing, decreasing, remain static

 

Types	CountPerTimeInterval32, CountPerTimeInterval64
Description	Usually used to describe the average count of items in a queue; if you have 0 items at the beginning, and 10 items after 5 seconds, then the rate would be displayed as 2.
Example	Monitoring a worker queue that contains jobs to run in the background
Displays as	average count change per time frame
Composite	no
Monotonicity	increasing, decreasing, remain static

Note

I found the information about CountPerTimeInterval somewhere on the internet. However, in my test I couldn’t get it working properly. The values of this counter would display as extremely small in Performance Monitor; something like 10.5E-06 – although it should be something like 10.5. Also Performance Monitor doesn’t seem capable of displaying negative values. They are necessary however when the queue handles requests faster than new requests get placed into it.

Types	SampleCounter
Description	Shows the average number of operations completed in one second (according to MSDN). Seems to be identical to RateOfCountsPerSecond (see below).
Example	Web requests served per second; for each served request, you would call Increment() on the counter
Displays as	average operation per second (during the last time frame)
Composite	no
Monotonicity	increasing, decreasing, remain static

Rate Counters ∞

Displays: rate of item count growth

Types	RateOfCountsPerSecond32, RateOfCountsPerSecond64
Description	Used to display how many items were – in average – processed per second during the last time frame. Seems to be identical to SampleCounter.
Example	Web requests served per second; for each served request, you would call Increment() on the counter
Displays as	average item per second (during the last time frame)
Composite	no
Monotonicity	increasing, decreasing, remain static

Percentage (of Time) Counters ∞

Displays: calculated values as a percentage

Types	CounterTimer, CounterTimerInverse, Timer100Ns, Timer100NsInverse
Description	Used to display the percent of time that a component is active (CounterTimer) or inactive (CounterTimerInverse).
Example	% of time an operation is running; you’d measure the time the operation takes to execute and then increase the counter’s value by this amount
Displays as	% of time a component was active during the last second (or other time frame)
Composite	no
Monotonicity	increasing, decreasing, remain static

Notes:

• CounterTimerInverse is like CounterTimer but measures how long the component is inactive. So, you’d measure the time from when the component became inactive to the next time it becomes active and increase the counter’s value by this amount.

• For CounterTimer and CounterTimerInverse, use Stopwatch.ElapsedTicks as counter value. For Timer100Ns and Timer100NsInverse, use DateTime.Ticks instead. (Note that these ticks have different lengths, as stated here.)

Types	CounterMultiTimer, CounterMultiTimerInverse, CounterMultiTimer100Ns, CounterMultiTimer100NsInverse
Description	Work exactly as their non-multi counterparts (e.g. CounterTimer for CounterMultiTimer), except that the result is divided by CounterMultiBase
Example	% of time an operation is running, if multiple calls to the operation can run in parallel; you’d measure the time the operation takes to execute and then increase the counter’s value by this amount; CounterMultiBase would be set to the number of parallel operations
Displays as	% of time a component was active during the last second (or other time frame)
Composite	yes (CounterMultiBase)
Monotonicity	increasing, decreasing, remain static

 

Types	SampleFraction
Description	Average ratio during the last time frame in percent
Example	Average ratio (%) of successful operations during the last time frame; you would increment SampleBase for every operation, and SampleFraction for each successful one.
Displays as	average ratio in %
Composite	yes (SampleBase)
Monotonicity	increasing, decreasing, remain static

Difference Counters ∞

Displays: difference between value at the beginning and the end of the time frame

Types	CounterDelta32, CounterDelta64
Description	Displays the difference between the raw value at the beginning and the end of the measured time frame
Example	Anything you need to display as difference
Displays as	difference
Composite	no
Monotonicity	increasing, decreasing, remain static

Note

Performance Monitor can’t display negative values.

Types	ElapsedTime
Description	Time in seconds since the counter was created sometime in the past. Note that you can’t set the value of this counter manually; it automatically increases.
Example	System up time
Displays as	seconds
Composite	no
Monotonicity	increasing, decreasing, remain static

Note

I have no clue what start time is chosen for the counter. It’s certainly not the time the counter was created. In my example, where I created the counter just a couple of seconds ago, it already had a value of about 27 hours (was even longer than my system up time).

Example Code ∞

Here’s an example project that demonstrates the various performance counters:

PerformanceCounters.zip (15 KB)