Would looping Thread.Sleep() be bad for performance when used to pause a thread?

Question

There is (or there has been) a lot of talk about wether it's good or bad to use the Thread.Sleep() method. From what I understand it is mainly to be used for debugging purposes.

Now I wonder: is it bad to use for my specific purpose, that is, constantly looping it to be able to pause/resume the thread? I do this because I want to pause a thread that performs I/O operations and be able to resume it in a simple way.

The I/O operations are basically just writing blocks of 4096 bytes to a file until all the data has been written to it. Since the file might be large and take a long time I want to be able to pause the operation (in case it would start eating much system resources).

My code, VB.NET version:

'Class level.
Private BytesWritten As Long = 0
Private Pause As Boolean = False

'Method (thread) level.
While BytesWritten < [target file size]
    ...write 4096 byte buffer to file...

    While Pause = True
        Thread.Sleep(250)
    End While

    ...do some more stuff...
End While

C# equivalent:

//Class level.
long bytesWritten = 0;
bool pause = false;

//Method (thread) level.
while(bytesWritten < [target file size]) {
    ...write 4096 byte buffer to file...

    while(pause == true) {
        Thread.Sleep(250);
    }

    ...do some more stuff...
}

I have heard about ResetEvents and I know a little bit about what they do, but I have never really looked much into them.

Answer 1

I think, based on the description, I'd do this

'Class level.
Private BytesWritten As Long = 0
Private NotPaused As New Threading.ManualResetEvent(True)

The change in the variable name is fitting since this is how it would be used

    'Method (thread) level.
     While BytesWritten < [target file size]
        '...write 4096 byte buffer to file...

        NotPaused.WaitOne(-1)

        '...do some more stuff...
    End While

To make the loop pause do this

    NotPaused.Reset()

and to continue

    NotPaused.Set()

Answer 2

In .NET there’s no reason to use Thread.Sleep besides trying to simulate lengthy operations while testing and / or debugging on an MTA thread as it will block.

Perhaps another option would be to use the TPL. Since you don't want to block you can use Task.Delay. As you probably know, a Task represents an asynchronous operation.