How to increase the maximum number of child processes that can be spawned by a windows service — desktop heap limits

Question

Q: I have a windows service that spawns a lot of child processes. There seems to be some limit, around 100, where the process cannot be launched. The CreateProcess() call

Answer 1

We had many Remote Desktop servers we needed to test this on, so we wrote a powershell script to query AD for our RD servers and then apply this registry change. Enjoy

   $newValue = "%SystemRoot%\system32\csrss.exe ObjectDirectory=\Windows SharedSection=1024,20480,2048 Windows=On SubSystemType=Windows ServerDll=basesrv,1 ServerDll=winsrv:UserServerDllInitialization,3 ServerDll=sxssrv,4 ProfileControl=Off MaxRequestThreads=16"
$origValue = "%SystemRoot%\system32\csrss.exe ObjectDirectory=\Windows SharedSection=1024,20480,768 Windows=On SubSystemType=Windows ServerDll=basesrv,1 ServerDll=winsrv:UserServerDllInitialization,3 ServerDll=sxssrv,4 ProfileControl=Off MaxRequestThreads=16"

if ($update) {
    Clear-Variable update
}

$updateConfirm= [System.Windows.Forms.MessageBox]::Show("Update Desktop Heap Limitation to 2048?" , "Status" , 4) 
if ($updateConfirm -eq "YES" ) {
    $update = $true
} else { 
    $revertConfirm= [System.Windows.Forms.MessageBox]::Show("Revert Desktop Heap Limitation to 768?" , "Status" , 4) 
    if ($revertConfirm -eq "YES" ) {
        $update = $false
    } 
}

if (($updateConfirm -ne "YES") -and ($revertConfirm -ne "YES")) {
    Write-Host "User did not specify whether to update or revert Desktop Heap Limitation. Exiting Setup."
    Read-Host "Press Enter to exit."
    break
}

#Import Active Directory PowerShell module
if (Test-Path C:\Users\${env:USERNAME}\Documents\WindowsPowerShell\Modules\ActiveDirectory\ActiveDirectory.psm1) {
    Import-Module ActiveDirectory -prefix AD
} else {
    $s = New-PSSession -computerName DC01WDC01
    Invoke-command { import-module ActiveDirectory } -session $s
    Export-PSSession -session $s -commandname *-AD* -outputmodule ActiveDirectory -allowclobber
    Import-Module ActiveDirectory -prefix AD
    Remove-PSSession -session $s
}

$servers =  Get-ADADComputer -Filter {(Name -Like "RDS*")}  | Select -Expand Name

foreach ($server in $servers) {
    Write-Host "Working on $server" -ForegroundColor Magenta
    if(!(Test-Connection -ComputerName $server -Count 1 -quiet)) {
        Write-Warning "$server : Offline"
        Continue
    }

    if ($update -eq $true) {
        Invoke-Command -ComputerName $server -ArgumentList $newValue -ScriptBlock {
            Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager\SubSystems" -Name "Windows" -Value $args[0]
            $result = Get-ItemProperty "HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager\SubSystems" | SELECT Windows
            if ($result.Windows -like "*SharedSection=1024,20480,2048*") {
                Write-Host "Successfully reverted Desktop Heap Limit to 2048" -ForegroundColor Green
            } else {
                Write-Warning "Update to registry value unsuccessful on $env:ComputerName" 
            }              
        }
    } elseif ($update -eq $false) {
        Invoke-Command -ComputerName $server -ArgumentList $origValue -ScriptBlock {
            Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager\SubSystems" -Name "Windows" -Value $args[0]
            $result = Get-ItemProperty "HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager\SubSystems" | SELECT Windows    
            if ($result.Windows -like "*SharedSection=1024,20480,768*") {
                Write-Host "Successfully reverted Desktop Heap Limit to 768" -ForegroundColor Green
            } else {
                Write-Warning "Update to registry value unsuccessful on $env:ComputerName" 
            }       
        }
    }
}