Performance Footprint of PowerShell Logon Scripts

PowerShell is a popular and extremely versatile tool, but is it a good idea to use PowerShell in logon scripts? Let’s try to find out!

Setting the Stage

I am going to compare the resource utilization of the following languages frequently used with logon scripts:

  • Batch
  • VBScript
  • PowerShell

How do you find the logon script’s duration and resource footprint? Such data is normally not too easy to come by, but uberAgent easily makes these and other logon metrics readily available.

Test Platform

All tests were performed on a virtual Windows Server 2012 R2, fully patched as of May 2015. Additional software: Citrix XenApp 7.6 VDA and uberAgent. The VM was equipped with 1 vCPU.

All measurements were taken in steady state, i.e. the machine had been booted up well in advance and I ignored the first logon because that basically puts all executables and DLLs from disk into RAM. During subsequent logons the disk is not used very much any more since all required files can be found in the operating system’s file system cache in RAM.

Test Scripts

I was interested in language overhead. That is why I was testing with very simple scripts that write the username to a text file.

Batch

Writing the username to a file is a one-liner in batch:

echo %username% > %temp%\username.txt

PowerShell

It is a one-liner in PowerShell, too:

$env:username > $env:temp\username2.txt

VBScript

VBScript requires an entire program to be written to accomplish the same task:

Set wshShell = CreateObject( "WScript.Shell" )
username = wshShell.ExpandEnvironmentStrings("%username%")
outFileName = wshShell.ExpandEnvironmentStrings("%temp%") & "\usernamevbs.txt"
Set outFile = CreateObject("Scripting.FileSystemObject").OpenTextFile(outFileName,2,true)
outFile.WriteLine(username)
outFile.Close

Results

Script Runtime

The batch file and the VBScript are in the 0.3 to 0.4 second range, whereas the PowerShell script takes a whopping 4.5 seconds to execute. Factor batch – PowerShell: 16x.

PowerShell logon script performance - runtime

CPU Usage

The batch file and the VBScript are in the 60 to 80 CPU ms range, whereas the PowerShell script consumes 1,123 CPU ms. Factor VBScript – PowerShell: 18x.

PowerShell logon script performance - CPU time

Memory Consumption

The batch file and the VBScript are in the 20 to 24 MB range, whereas the PowerShell script needs 98 MB RAM. Factor batch – PowerShell: 5x.

PowerShell logon script performance - RAM

Conclusion

The total duration of the user logon is important to good user experience. With Citrix XenApp published applications logon speed even is critical. Logon script performance is often underestimated, partly due to the fact that Windows does not tell you how long a logon script took to execute and what the resource footprint was. uberAgent adds much needed visibility by providing detailed information about all aspects of the user logon.

PowerShell is a great tool, but its resource footprint and runtime overhead make it a difficult recommendation for logon scripts which run at a point in time where many processes are competing for resources. Logon delays badly affect user experience. Any tools added to this phase should be as efficient as possible.

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8 Responses to Performance Footprint of PowerShell Logon Scripts

  1. ramblingcookiemonster September 7, 2015 at 16:42 #

    Hi Helge!

    Ouch – which versions of Windows Management Framework and Windows were these tests run under?

    • Helge Klein September 7, 2015 at 16:56 #

      The tests were run on a fully patched (as of May 2015) Server 2012 R2.

  2. RichardP September 7, 2015 at 23:18 #

    Wow – totally the opposite of what I would have expected. Back to batch it is!

  3. xpclient September 8, 2015 at 10:15 #

    Kind of expected, isn’t it? SetACL Studio should also be rewritten in C++ in my opinion.

  4. Michel de Rooij September 8, 2015 at 11:01 #

    I won’t argue over PowerShell’s resource requirements, however apart from that the other important statement you made is: “VBScript requires an entire program to be written to accomplish the same task”. Compare PowerShell’s possibilities and maintainability against maintaining pages of VB Scripts or batch files (KiXtart anyone?) and the (hidden) costs. Hardware is cheap.

  5. Ton September 8, 2015 at 20:52 #

    I think you are jumping to conclusions a bit here. One command does not a script make!
    I guess a large part of the time you are measuring is loading of Powershell itself. Once it is loaded it could be a lot faster actually executing commands, so if you have a couple of pages of logon script it could be kicking Batch backside. Honestly I don’t think it will but I would surprised if the difference between Batch and PS is not a lot smaller with a large script. The strength of Batch is small footprint, fast loading and execution. Powershell has a lot more functionality but that results in a larger executable (+ dependencies) to be loaded into RAM, thus the longer loading time. Different horses etc.
    And 4.5 seconds? I’m sure it’s a test environment you are testing on but I just ran your script on my laptop, and it can’t have taken more than two seconds (no UberAgent here for exact timing, sorry mate). The actual command execution took 39 ms. If I put the same command in the script three times, the second and third time the command is executed takes only 3 ms.

    But all my bitching aside, logon scripts are so last century anwyay :-)

  6. ramblingcookiemonster September 11, 2015 at 18:10 #

    Hi Helge!

    Me again : )

    Do you know whether the ngen scheduled tasks had run prior to these logons? Micah Rairdon mentioned this: https://social.technet.microsoft.com/Forums/windows/en-US/c777c2dc-0014-4ec6-b2ba-9711121f63d5/powershell-slow-to-start-on-clean-install-with-empty-profile-present?forum=w8itprogeneral

    Cheers!

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