PowerShell 作业与启动进程

Question

我制作了一个小诊断脚本，保存在 $profile 中.在收集 CPU 名称时，我发现该命令大约需要 4 秒 (Get-WmiObject -Class Win32_Processor).Name .所以我想我会尝试 PowerShell Jobs 并且虽然我认为它们对于长时间的后台作业非常有用，但如果您只想在后台快速获取一小部分信息，则初始化时间很尴尬(例如 2-3 秒每个作业)所以我想我会使用 Start-Process 在我的脚本的其余部分运行时转储临时文件中的值。我想我这样做是正确的，但是如果你运行这个函数 3 或 4 次，你会注意到 CPU 名称没有被填充。

• 像这样使用Start-Process 是最佳选择，还是有人有更快的方法在后台并行启动小作业？我知道有一种 .NET 方法可以做到这一点(但从我所看到的来看，它似乎非常复杂)？

• 你知道为什么我的“等待文件创建并在访问它之前非零”经常失败吗？

function sys {
    $System = get-wmiobject -class "Win32_ComputerSystem"
    $Mem = [math]::Ceiling($System.TotalPhysicalMemory / 1024 / 1024 / 1024)

    $wmi = gwmi -class Win32_OperatingSystem -computer "."
    $LBTime = $wmi.ConvertToDateTime($wmi.Lastbootuptime)
    [TimeSpan]$uptime = New-TimeSpan $LBTime $(get-date)
    $s = "" ; if ($uptime.Days -ne 1) {$s = "s"}
    $uptime_string = "$($uptime.days) day$s $($uptime.hours) hr $($uptime.minutes) min $($uptime.seconds) sec"

    $temp_cpu = "$($env:TEMP)\ps_temp_cpu.txt"
    $temp_cpu_cores = "$($env:TEMP)\ps_temp_cpu_cores.txt"
    $temp_cpu_logical = "$($env:TEMP)\ps_temp_cpu_logical.txt"
    rm -force $temp_cpu -EA silent ; rm -force $temp_cpu_cores -EA silent ; rm -force $temp_cpu_logical -EA silent
    Start-Process -NoNewWindow -FilePath "powershell.exe" -ArgumentList "-NoLogo -NoProfile (Get-WmiObject -Class Win32_Processor).Name > $temp_cpu"
    Start-Process -NoNewWindow -FilePath "powershell.exe" -ArgumentList "-NoLogo -NoProfile (Get-WmiObject -Class Win32_Processor).NumberOfCores > $temp_cpu_cores"
    Start-Process -NoNewWindow -FilePath "powershell.exe" -ArgumentList "-NoLogo -NoProfile (Get-WmiObject -Class Win32_Processor).NumberOfLogicalProcessors > $temp_cpu_logical"
    ""
    "Hostname:          $($System.Name)"
    "Domain:            $($System.Domain)"
    "PrimaryOwner:      $($System.PrimaryOwnerName)"
    "Make/Model:        $($System.Manufacturer) ($($System.Model))"  #     "ComputerModel:  $((Get-WmiObject -Class:Win32_ComputerSystem).Model)"
    "SerialNumber:      $((Get-WmiObject -Class:Win32_BIOS).SerialNumber)"
    "PowerShell:        $($PSVersionTable.PSVersion)"
    "Windows Version:   $($PSVersionTable.BuildVersion)"
    "Windows ReleaseId: $((Get-ItemProperty -Path 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion' -Name 'ReleaseId').ReleaseId)"
    "Display Card:      $((Get-WmiObject -Class:Win32_VideoController).Name)"
    "Display Driver:    $((Get-WmiObject -Class:Win32_VideoController).DriverVersion)"
    "Display ModelDesc: $((Get-WmiObject -Class:Win32_VideoController).VideoModeDescription)"
    "Last Boot Time:    $([Management.ManagementDateTimeConverter]::ToDateTime((Get-WmiObject Win32_OperatingSystem | select 'LastBootUpTime').LastBootUpTime))"   # $(wmic OS get LastBootupTime)
    "Uptime:            $uptime_string"
    # ipconfig | sls IPv4
    Get-Netipaddress | where AddressFamily -eq IPv4 | select IPAddress,InterfaceIndex,InterfaceAlias | sort InterfaceIndex

    # Get-PSDrive | sort -Descending Free | Format-Table
    # https://stackoverflow.com/questions/37154375/display-disk-size-and-freespace-in-gb
    # https://www.petri.com/checking-system-drive-free-space-with-wmi-and-powershell
    # https://www.oxfordsbsguy.com/2017/02/08/powershell-how-to-check-for-drives-with-less-than-10gb-of-free-diskspace/
    # Get-Volume | Where-Object {($_.SizeRemaining -lt 10000000000) -and ($_.DriveType -eq “FIXED”) -and ($_.FileSystemLabel -ne “System Reserved”)}
    gwmi win32_logicaldisk | Format-Table DeviceId, VolumeName, @{n="Size(GB)";e={[math]::Round($_.Size/1GB,2)}},@{n="Free(GB)";e={[math]::Round($_.FreeSpace/1GB,2)}}

    # Note: -EA silent on Get-Item otherwise get an error
    while (!(Test-Path $temp_cpu)) { while ((Get-Item $temp_cpu -EA silent).length -eq 0kb) { Start-Sleep -Milliseconds 500 } }
    "CPU:               $(cat $temp_cpu)"
    while (!(Test-Path $temp_cpu_cores)) { while ((Get-Item $temp_cpu_cores -EA silent).length -eq 0kb) { Start-Sleep -Milliseconds 500 } }
    "CPU Cores:         $(cat $temp_cpu_cores)"
    while (!(Test-Path $temp_cpu_logical)) { while ((Get-Item $temp_cpu_logical -EA silent).length -eq 0kb) { Start-Sleep -Milliseconds 500 } }
    "CPU Logical:       $(cat $temp_cpu_logical)"
    rm -force $temp_cpu -EA silent ; rm -force $temp_cpu_cores -EA silent ; rm -force $temp_cpu_logical -EA silent
    "Memory:            $(Get-CimInstance Win32_PhysicalMemory | Measure-Object -Property capacity -Sum | Foreach {"{0:N2}" -f ([math]::round(($_.Sum / 1GB),2))}) GB"
    ""
    "Also note the 'Get-ComputerInfo' Cmdlet (has more info but slower to run)"
    ""
}

Answer 1

要在 powershell 后台运行作业，有以下 3 种方法

1. Invoke-Command[3] -scriptblock { script }  -asJob -computername localhost
2. Start-Job[2] -scriptblock { script }
3. Start-Process[1] powershell {script} 

If you truly want to run things in the background with each job being independent of each other, you'll have to think about using the first or second option as neither of them require the output to be written to a file.

Invoke-Command starts a new session with the system and runs the job in a new instance.

Start-Job creates a new job in the background under a new powershell instance, takes a little more time to allocate the resources and start the process. Just like start-process, Start-Job will run the job in a separate powershell.exe instance.

Start-Process requires you to redirect the standard output to a file^[1]. You have to rely on the performance of the disk and how fast your reads and writes are. You also have to ensure that no more than one thread is reading/writing to the output of this process.

Recommendation I found Invoke-Command to be the fastest when running 100 concurrent jobs to get the processor info. This option does require you to provide -ComputerName which then requires you to be an admin to start a winrm Session with localhost. If you dont output the job information while creating the jobs, it does not take away any significant time.

Start-Job and Invoke-Command both took about a second to get the processor info and running 100 concurrent jobs to get the same thing took some overhead.

$x = 0..100 | Invoke-Command -computername localhost -scriptblock { script } -asJob
$x | % { $_ | wait-job | out-null }
$output = $x | % { $_ | Receive-Job}
# You can run measure-object, sort-object, etc as well

[1] Start-Process

RedirectStandardOutput: Specifies a file. This cmdlet sends the output generated by the process to a file that you specify. Enter the path and filename. By default, the output is displayed in the console.

[2] Start-Job

The Start-Job cmdlet starts a PowerShell background job on the local computer. ... A PowerShell background job runs a command without interacting with the current session.

[3] Invoke-Command

The Invoke-Command cmdlet runs commands on a local or remote computer and returns all output from the commands, including errors. ... To run a command in a background job, use the AsJob parameter