How to: Instrument a dynamically compiled ASP.NET web application and collect detailed timing data with the profiler by using the command line

This article describes how to use Visual Studio Profiling Tools command-line tools to collect detailed timing data for a dynamically compiled ASP.NET application by using the instrumentation profiling method.


To get the path to the profiling tools, see Specify the path to command line tools. On 64-bit computers, both 64-bit and 32-bit versions of the tools are available. To use the profiler command-line tools, you must add the tools path to the PATH environment variable of the Command Prompt window or add it to the command itself.

To collect performance data from a ASP.NET web application, you modify the web.config file of the target application to enable the VSInstr.exe tool to instrument the dynamically compiled application files. You then use the VSPerfCLREnv.cmd tool to set the appropriate environment variables on the web server to enable profiling, and then restart the computer.

Start the profiler and then run the target application. While the profiler is attached to the application, you can pause and resume data collection. When you finish profiling, close the application, close the Internet Information Services (IIS) worker process, and then shut down the profiler. When you have completed your profiling work, restore the web.config file and the Web server to their original states.

Configure the ASP.NET web application and the web server

  1. Modify the web.config file of the target application. See How to: Modify web.config files to instrument and profile dynamically compiled ASP.NET web applications.

  2. Open a Command Prompt window.

  3. Initialize the profiling environment variables. Type:

    VSPerfClrEnv /globaltraceon

    • /globaltraceon enables profiling by using the instrumentation method.
  4. Restart the computer.

Run the profiling session

  1. Open a Command Prompt window.

  2. Start the profiler. Type:

    VSPerfCmd /start :trace /output : OutputFile [Options]

    • The /start:trace option initializes the profiler.

    • The /output:OutputFile option is required with /start. OutputFile specifies the name and location of the profiling data (.vsp) file.

      You can use any of the following options with the /start:trace option.


      The /user and /crosssession options are usually required for ASP.NET applications.

      Option Description
      /user :[Domain\]UserName Specifies the domain and user name of the account that owns the ASP.NET worker process. This option is required if the process is running as a user other than the logged-on user. The process owner is listed in the User Name column on the Processes tab of Windows Task Manager.
      /crosssession Enables profiling of processes in other logon sessions. This option is required if the ASP.NET application is running in a different session. The session identifier is listed in the Session ID column on the Processes tab of Windows Task Manager. /CS can be specified as an abbreviation for /crosssession.
      /globaloff Starts the profiler with data collection paused. Use /globalon to resume profiling.
      /counter : Config Collects information from the processor performance counter that is specified in Config. Counter information is added to the data that is collected at each profiling event.
      /wincounter : WinCounterPath Specifies a Windows performance counter to be collected during profiling.
      /automark : Interval Use with /wincounter only. Specifies the number of milliseconds between Windows performance counter collection events. Default is 500 ms.
      /events : Config Specifies an Event Tracing for Windows (ETW) event to be collected during profiling. ETW events are collected in a separate (.etl) file.
  3. Start the ASP.NET web application in the typical way.

Control data collection

While the target application is running, you can control data collection by starting and stopping the writing of data to the profiler data file by using VSPerfCmd.exe options. Controlling data collection enables you to collect data for a specific part of program execution, such as starting or shutting down the application.

  • The following pairs of options start and stop data collection. Specify each option on a separate command line. You can turn data collection on and off multiple times.

    Option Description
    /globalon /globaloff Starts (/globalon) or stops (/globaloff) data collection for all processes.
    /processon : PID /processoff : PID Starts (/processon) or stops (/processoff) data collection for the process specified by the process ID (PID).
    /threadon : TID /threadoff : TID Starts (/threadon) or stops (/threadoff) data collection for the thread specified by the thread ID (TID).
  • You can also use the VSPerfCmd.exe/mark option to insert a profiling mark into the data file. The /mark command adds an identifier, a time stamp, and an optional user-defined text string. Marks can be used to filter the data in profiler reports and data views.

End the profiling session

To end a profiling session, close the target ASP.NET web application, reset IIS to stop the profiled process, and then shut down the profiler.

  1. Close the ASP.NET web application.

  2. Close the ASP.NET worker process by resetting Internet Information Services (IIS). Type:

    IISReset /stop

  3. Shut down the profiler. Type:

    VSPerfCmd /shutdown

  4. Restart IIS. Type:

    IISReset /start

Restore the application and computer configuration

When you have completed all profiling, replace the web.config file, clear the profiling environment variables, and restart the computer to restore the application and server to the states that they were in before profiling.

  1. Replace the web.config file with a copy of the original file.

  2. Clear the profiling environment variables. Type:

    VSPerfCmd /globaloff

  3. Restart the computer.

See also

Profile ASP.NET web applications Instrumentation method data views