Timers Are Not What They Seem

Analysis of the .NET timers with 1ms tick size:

• System.Timers.Timer
• System.Threading.Timer
• Multimedia Timer imported from winmm.dll
• TwinCAT 3. Soft Real-Time System
• Dedicated Thread
  • Thread.Sleep(1)
  • SpinWait 10000us
  • Thread.Sleep(0)
  • Without idle between ticks
  • Interval by Stopwatch

If you don't have Jupiter Notebooks installed locally, just use online Jupyter NBViewer

Results

• System.Timers.Timer and System.Threading.Timer are limited with 15.6 ms by default.
• Multimedia Timer. Always stable but legacy.
• TwinCAT3 notifications. Not good at client side.
• Independed threads. Not stable at heavy load.

Conclusion. Should use legacy Multimedia Timer or modern real-time systems like TC3.

Goodreads

• Acquiring high-resolution time stamps -- 31-05-2018

• Results of some quick research on timing in Win32 by Ryan Geiss -- 16 August 2002 (...with updates since then)

• Real-Time Systems with Microsoft Windows CE 2.1 -- 06/29/2006

• pdf A Real Time Operating Systems (RTOS) Comparison

• docx Timers, Timer Resolution, and Development of Efficient Code -- June 16, 2010

CPU Burner

Loads all cpu's cores w/ 100%

while (!token.IsCancellationRequested) {
    Parallel.For( 0, Environment.ProcessorCount, ( i ) => {
        double a = 1000.0;
        for (int j = 0; j < 10_000_000; j++) {
            if (token.IsCancellationRequested)
                break;

            a /= j * (i + 1);
        }
    } );
}

See CpuBurner.cs

Multimedia Timer

Legacy functions from early versions of Windows

[DllImport( "winmm.dll", SetLastError = true, EntryPoint = "timeSetEvent" )]
internal static extern UInt32 TimeSetEvent( UInt32 msDelay, UInt32 msResolution, MultimediaTimerCallback callback, ref UInt32 userCtx, UInt32 eventType );

[DllImport( "winmm.dll", SetLastError = true, EntryPoint = "timeKillEvent" )]
internal static extern void TimeKillEvent( UInt32 uTimerId );

See MultimediaTimer.cs

TwinCAT 3. Soft Real-Time System

RT-system Side

System tick and PLC-Runtime both are 1 millisecond.

PROGRAM MAIN
VAR
    tick: BOOL;
END_VAR

tick := NOT tick;

END_PROGRAM

Client Side

AdsClient client = new AdsClient();
client.Connect( AmsPort.R0_RTS + 1 );

client.AdsNotification += (s,e) => DoTick();
var notiSets = new NotificationSettings( AdsTransMode.OnChange, 1, 0 );
var h_tick = client.AddDeviceNotification( "MAIN.tick", 1, notiSets, null );