System performance counters in Application Insights

Windows provides a wide variety of performance counters such as CPU occupancy, memory, disk, and network usage. You can also define your own performance counters. Performance counters collection is supported as long as your application is running under IIS on an on-premises host, or virtual machine to which you have administrative access. Though applications running as Azure Web Apps don't have direct access to performance counters, a subset of available counters are collected by Application Insights.

View counters

The Metrics pane shows the default set of performance counters.

Performance counters reported in Application Insights

The current default counters that are configured to be collected for ASP.NET web applications are:

  • % Process\Processor Time
  • % Process\Processor Time Normalized
  • Memory\Available Bytes
  • ASP.NET Requests/Sec
  • .NET CLR Exceptions Thrown / sec
  • ASP.NET ApplicationsRequest Execution Time
  • Process\Private Bytes
  • Process\IO Data Bytes/sec
  • ASP.NET Applications\Requests In Application Queue
  • Processor(_Total)\% Processor Time

The current default counters that are configured to be collected for ASP.NET Core web applications are:

  • % Process\Processor Time
  • % Process\Processor Time Normalized
  • Memory\Available Bytes
  • Process\Private Bytes
  • Process\IO Data Bytes/sec
  • Processor(_Total)\% Processor Time

Add counters

If the performance counter you want isn't included in the list of metrics, you can add it.

  1. Find out what counters are available in your server by using this PowerShell command on the local server:

    Get-Counter -ListSet *

    (See Get-Counter.)

  2. Open ApplicationInsights.config.

    • If you added Application Insights to your app during development, edit ApplicationInsights.config in your project, and then redeploy it to your servers.
  3. Edit the performance collector directive:

        <Add Type="Microsoft.ApplicationInsights.Extensibility.PerfCounterCollector.PerformanceCollectorModule, Microsoft.AI.PerfCounterCollector">
            <Add PerformanceCounter="\Objects\Processes"/>
            <Add PerformanceCounter="\Sales(photo)\# Items Sold" ReportAs="Photo sales"/>


ASP.NET Core applications do not have ApplicationInsights.config, and hence the above method is not valid for ASP.NET Core Applications.

You can capture both standard counters and those you've implemented yourself. \Objects\Processes is an example of a standard counter that is available on all Windows systems. \Sales(photo)\# Items Sold is an example of a custom counter that might be implemented in a web service.

The format is \Category(instance)\Counter", or for categories that don't have instances, just \Category\Counter.

ReportAs is required for counter names that do not match [a-zA-Z()/-_ \.]+ - that is, they contain characters that are not in the following sets: letters, round brackets, forward slash, hyphen, underscore, space, dot.

If you specify an instance, it will be collected as a dimension "CounterInstanceName" of the reported metric.

Collecting performance counters in code for ASP.NET Web Applications or .NET/.NET Core Console Applications

To collect system performance counters and send them to Application Insights, you can adapt the snippet below:

    var perfCollectorModule = new PerformanceCollectorModule();
    perfCollectorModule.Counters.Add(new PerformanceCounterCollectionRequest(
      @"\Process([replace-with-application-process-name])\Page Faults/sec", "PageFaultsPerfSec"));

Or you can do the same thing with custom metrics you created:

    var perfCollectorModule = new PerformanceCollectorModule();
    perfCollectorModule.Counters.Add(new PerformanceCounterCollectionRequest(
      @"\Sales(photo)\# Items Sold", "Photo sales"));

Collecting performance counters in code for ASP.NET Core Web Applications

Modify ConfigureServices method in your Startup.cs class as below.

using Microsoft.ApplicationInsights.Extensibility.PerfCounterCollector;

    public void ConfigureServices(IServiceCollection services)

        // The following configures PerformanceCollectorModule.
  services.ConfigureTelemetryModule<PerformanceCollectorModule>((module, o) =>
                // the application process name could be "dotnet" for ASP.NET Core self-hosted applications.
                module.Counters.Add(new PerformanceCounterCollectionRequest(
    @"\Process([replace-with-application-process-name])\Page Faults/sec", "DotnetPageFaultsPerfSec"));

Performance counters in Analytics

You can search and display performance counter reports in Analytics.

The performanceCounters schema exposes the category, counter name, and instance name of each performance counter. In the telemetry for each application, you'll see only the counters for that application. For example, to see what counters are available:

Performance counters in Application Insights analytics

('Instance' here refers to the performance counter instance, not the role, or server machine instance. The performance counter instance name typically segments counters such as processor time by the name of the process or application.)

To get a chart of available memory over the recent period:

Memory timechart in Application Insights analytics

Like other telemetry, performanceCounters also has a column cloud_RoleInstance that indicates the identity of the host server instance on which your app is running. For example, to compare the performance of your app on the different machines:

Performance segmented by role instance in Application Insights analytics

ASP.NET and Application Insights counts

What's the difference between the Exception rate and Exceptions metrics?

  • Exception rate is a system performance counter. The CLR counts all the handled and unhandled exceptions that are thrown, and divides the total in a sampling interval by the length of the interval. The Application Insights SDK collects this result and sends it to the portal.

  • Exceptions is a count of the TrackException reports received by the portal in the sampling interval of the chart. It includes only the handled exceptions where you have written TrackException calls in your code, and doesn't include all unhandled exceptions.

Performance counters for applications running in Azure Web Apps

Both ASP.NET and ASP.NET Core applications deployed to Azure Web Apps run in a special sandbox environment. This environment does not allow direct access to system performance counters. However, a limited subset of counters are exposed as environment variables as described here. Application Insights SDK for ASP.NET and ASP.NET Core collects performance counters from Azure Web Apps from these special environment variables. Only a subset of counters are available in this environment, and the full list can be found here.

Performance counters in ASP.NET Core applications

Support for performance counters in ASP.NET Core is limited:

  • SDK versions 2.4.1 and later collect performance counters if the application is running in Azure Web Apps (Windows).
  • SDK versions 2.7.1 and later collect performance counters if the application is running in Windows and targets NETSTANDARD2.0 or later.
  • For applications targeting the .NET Framework, all versions of the SDK support performance counters.
  • SDK Versions 2.8.0 and later support cpu/memory counter in Linux. No other counter is supported in Linux. The recommended way to get system counters in Linux (and other non-Windows environments) is by using EventCounters


Like other metrics, you can set an alert to warn you if a performance counter goes outside a limit you specify. Open the Alerts pane and click Add Alert.

Next steps