Induce system lag in vb.net

Question

I need to induce a variable amount of lag in vb.net. System should be noticeably slower.

I can raise the CPU usage of the program with infinite loops and some variable creation/assignments, but how can I actually cause lag?

I understand this is an odd request, but I appreciate any help and would appreciate it being taken seriously. This is NOT being used maliciously.

I'd like to have an "InvokeLag" sub which will perform an action to slow down the computer, the faster the function is called the faster it lags. The function should be as mundane as possible, not modifying anything or doing anything to cause damage other than simple lag.

Thanks for your help!

EDIT: Preferably only achieving this effect with crazy math operations and making variables and such. Nothing system if possible.

Answer 1

How about outsourcing your system's lag to another process altogether:

System.Diagnostics.Process.Start("Outlook.exe")

Seriously though, does the system need to be slowed by your process & its computations, or can you rely on other processes to generate the CPU usage? It depends on what you're trying to gauge. It sounds like increasing CPU usage to approach 100% is what you're targeting.

Perhaps call SysInfo, or Vista/Win7, call Windows Experience Index. I know you've updated your question with 'nothing system', but does it matter?

Answer 2

What about creating a new thread with the highest priority? Calculating Pi will never end and with a high priority it should lag your system down. If you have several processors you could start several threads to calculate pi or have a separate program that calculates pi and start several processes of it?

Public Class Test
    Shared Sub Main()

        Dim threadLag As Thread = _
            New Thread(AddressOf CalculatePi)
        threadLag.Name = "ThreadWait"
        threadLag.Priority = ThreadPriority.Highest
        threadLag.Start()
    End Sub

    Private Sub LagRoutine()
        While True
            Thread.SpinWait(10000)
        End While
    End Sub

End Class

or

Public Class Test
    Shared Sub Main()
        For i as Integer = 1 to 10
             Dim p As New Process("C:\MyLagProgram.exe")
             p.Start()
        Next i
    End Sub

End Class

CalculatePi

MSDN

Update:

I think Eric might have a good point about SpinWait and it might be more what you are looking for:

The SpinWait method is useful for implementing locks. Classes in the .NET Framework, such as Monitor and ReaderWriterLock, use this method internally. SpinWait essentially puts the processor into a very tight loop, with the loop count specified by the iterations parameter. The duration of the wait therefore depends on the speed of the processor.

Contrast this with the Sleep method. A thread that calls Sleep yields the rest of its current slice of processor time, even if the specified interval is zero. Specifying a non-zero interval for Sleep removes the thread from consideration by the thread scheduler until the time interval has elapsed.

There is no System IO, its basically just a tight loop which does not give up its processing time. I am sure if you used my suggestion of spawning several threads with the highest priority with Eric's suggestion SpinWait you would achieve what you are looking for. This would also reduce the amount of code you would need to write.

Answer 3

It might help if you defined lag. If you're just looking to spike the CPU, a couple of threads and some loops will do the trick (as you mentioned). You could also use the SpinWait() method on the System.Threading.Thread class.

However, from your post it sounds like that's not acceptable... perhaps that doesn't adequately simulate what you're going for? Are you looking to cause the hard drive to thrash a little bit? When I think of lag I generally think of the system paging back and forth between disk and memory. If that's the case, you could simulate all that IO yourself by reading and writing some large files of whatever (junk data).