What Thread sleep method is most precise: Monitor.Wait vs System.Timer vs DispatchTimer vs Threading.Timer

Question

What .NET object (or technique) is the most precise at launching a thread every XXX milliseconds? What are the tradeoffs?

For example:

        int maxDurationMs = 1000;
        while (true)
        {
            DateTime dt = DateTime.UtcNow;
            DoQuickStuff()
            TimeSpan duration1 =  DateTime.UtcNow - dt;
            int sleepTime = maxDurationMs - duration1.Milliseconds;
            if (sleepTime > 0)
                System.Threading.Thread.Sleep(sleepTime);
        }

or

       // CPU Intensive, but fairly accurate
       int maxDurationMs = 1000;
        while (true)
        {
            DateTime dt = DateTime.UtcNow;
            DoQuickStuff()
            while (true)
            {
                if (dt.AddMilliseconds(maxDurationMs) >= DateTime.UtcNow)
                    break;
            }
        }

Alternate methods of doing the same thing, but with varying degrees of accuracy and tradeoffs (CPU, etc)

• System.Timer
• DispatchTimer
• System.Threading.Timer
• Thread.Join
• .NET 4.0 Task
• Thread.Sleep()
• Monitor.Wait(obj, timespan)
• Multimedia Timers (thanks Brian Gideon)
• Win32 High Resolution timers
• Something else?

Answer 1

I have never actually used them myself, but Multimedia Timers are said to have the best resolution of any timer service in Windows. The .NET BCL does not have a wrapper for this timer service yet so you will have to do the P/Invoke calls yourself.

Another option might be to use Stopwatch together with some standard Thread.Sleep calls in a tight loop. I am not sure how much luck you would have with this approach, but it might be more accurate than a plain old Thread.Sleep call by itself. I have never tried it, but anything is worth a shot I suppose.

I did some experiments and I discovered that changing the thread priority to ThreadPriority.Highest made a considerable difference. It reduced the standard deviation of the interval by quite a bit on each technique I tried.

Answer 2

Don't use DateTime: its accuracy is limited to around 16ms on most systems. (See Eric Lippert's blog)

The most accurate method would be to have a dedicated thread running a while loop with a System.Diagnostics.Stopwatch object to count the time.

Even with the most precise and accurate timer in existance, raising an event exactly every x milliseconds is no simple task given the unpredictability of CPU time slices: I suggest looking into how games do their main loop (achieving a stable 30fps with lag compensation, for instance). A good example is OpenTK's GameWindow, specifically the RaiseUpdateFrame method.