Low Priority I/O @ PowerShell

PriorityHelper.cs

using System;
using System.Runtime.InteropServices;
using Microsoft.Win32.SafeHandles;

public static class PriorityHelper
{
    [DllImport("kernel32.dll", SetLastError = true)]
    static extern SafeProcessHandle OpenProcess(
         ProcessAccessFlags processAccess,
         bool bInheritHandle,
         int processId
    );

    [DllImport("ntdll.dll", SetLastError = true)]
    static extern int NtSetInformationProcess(SafeProcessHandle processHandle,
       PROCESS_INFORMATION_CLASS processInformationClass, IntPtr processInformation,
       int processInformationLength);

    [Flags]
    enum ProcessAccessFlags : uint
    {
        SetInformation = 0x00000200
    }

    enum PROCESS_INFORMATION_CLASS : uint
    {
        ProcessIoPriority = 33 // qs: ULONG
    };

    const uint LowIoPriority = 1u;

    public static bool SetLowPriorityIO(int procId)
    {
        using (var hProc = OpenProcess(ProcessAccessFlags.SetInformation, false, procId))
        {
            if (hProc.IsInvalid) return false;
            var ioPriority = IntPtr.Zero;
            try
            {
                var size = Marshal.SizeOf<uint>();
                ioPriority = Marshal.AllocHGlobal(size);
                Marshal.WriteInt32(ioPriority, (int)LowIoPriority);
                return NtSetInformationProcess(hProc, PROCESS_INFORMATION_CLASS.ProcessIoPriority, ioPriority, size) == 0;
            }
            finally
            {
                if (ioPriority != IntPtr.Zero) Marshal.FreeHGlobal(ioPriority);
            }
        }
    }
}

SetLowPriorityIO.ps1

Add-Type @"
using System;
using System.Runtime.InteropServices;
(snip)
    }
}
"@

[PriorityHelper]::SetLowPriorityIO($PID)