Максимально быстрое чтение очень большого файла

Imports System.IO
Imports System.IO.MemoryMappedFiles
 
Public Class Form1
    Dim strPathFile As String
    Dim line As String
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim count As Long
        Dim SW As New Stopwatch
 
        Dim ramCounter As New System.Diagnostics.PerformanceCounter("Memory", "Available MBytes")
        MsgBox(ramCounter.NextValue)
 
        Using mmf = MemoryMappedFile.CreateFromFile(strPathFile, FileMode.Open, "ImgA", 0)
            Using streamreader = New StreamReader(mmf.CreateViewStream)
                SW.Start()
                Do While streamreader.Peek >= 0
                    streamreader.ReadLine()
                    count = count + 1
                    If count Mod 1000 = 0 Then Me.Text = count - 1
                Loop
                Me.Text = count - 1
                SW.Stop()
                MsgBox(SW.Elapsed.Seconds & " сек.")
                streamreader.Dispose()
                mmf.Dispose()
            End Using
        End Using
    End Sub
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        If OpenFileDialog1.ShowDialog() = System.Windows.Forms.DialogResult.OK Then strPathFile = OpenFileDialog1.FileName ': Me.Text = strPathFile
    End Sub
End Class