Stateless Statemachine Framework and high CPU usage

Question

I'm using the Stateless Framework to create a StateMachine. My Main Application is a ConsoleApplication which calls the DataManager class, which calls the GetData function which starts a Task which then executes the Receiver function with the state machine.

My Problem is that I get about 50% CPU usage when the StateMachine runs! When I implement a StateMachine with a simple switch statement and the same Task it runs with a 0% CPU usage! Do I have a some coding error or is that the behaivor of the Stateless Framework?

The GetData function

public List<Byte[]> GetData()
{
    List<Byte> rawData = new List<Byte[]>();
    ReceiveTask = Task.Factory.StartNew<List<Byte[]>>(() => Receiver());
    //Wait until the Task is complete

    ReceiveTask.Wait();
    //return temp;
    rawData = ReceiveTask.Result;

    return rawData;
}

The DataManager class

public partial class DataManager 
{

int _expectedBlocks;

Byte[] _currentMessage = null;
Byte[] _firstMessage = null;
int _currentBlockNumber = 0;

enum State { Idle, Start, Next, Check, End }
enum Trigger { DataOK, DataRequest, ReceivingFirstBlock, ReceivingNextBlock, LastPacketReceived, WaitForNext }

Dictionary<int, Byte[]> _receivedData;

List<Byte[]> _outputList;

StateMachine<State, Trigger> _machine;


private List<Byte[]> Receiver()
{
    _currentMode = Mode.Receive;
    m_source.MessageReceivedEvent +=new EventHandler<WSANMessageResponseEventArgs>(m_source_MessageReceivedEvent);
    m_source.StartConnection();
    _machine = new StateMachine<State, Trigger>(State.Idle);

    _receivedData = new Dictionary<int, byte[]>();

    _outputList = new List<byte[]>();

    //Config StateMachine
    _machine.Configure(State.Idle)
        .OnEntry(() => OnIdle())
        .OnExit(() => ExitIdle())
        .Permit(Trigger.ReceivingFirstBlock, State.Start);

    _machine.Configure(State.Start)
        .OnEntry(() => OnStart())
        .Permit(Trigger.ReceivingNextBlock, State.Next);

    _machine.Configure(State.Next)
        .OnEntry(() => OnNext())
        .Permit(Trigger.WaitForNext, State.Start)
        .Permit(Trigger.LastPacketReceived, State.Check);

    _machine.Configure(State.Check)
        .OnEntry(() => OnCheck())
        .Permit(Trigger.DataOK, State.End)
        .Permit(Trigger.DataRequest, State.Idle);

    _machine.Configure(State.End)
        .OnEntry(() => OnEnd());


     while (_machine.State != State.End)
     {

     }
    _currentMode = Mode.Idle;
    return _outputList;
}

Regards Michael

IvoTops · Answer 1 · 2012-08-22T12:31:09.617

Change the wait loop

     while (_machine.State != State.End)
     {
         Thread.Sleep(10); // Only check once in a while
     }

Another way to do this very efficiently without looping;

Create a ManualResetEventSlim object;

 ManualResetEventSlim mre = new ManualResetEventSlim(false);

The Wait loop changes to

 mre.Wait(); // Waits untill the mre is signaled

And when the _machine.State becomes State.End it should call

 mre.Set();

which will signal the waiter and will cause the mre.Wait() to stop waiting

score 0 · Answer 2 · answered Oct 03 '12 at 14:26

Your CPU is 50% because you have 2 cores in it and your thread is consuming the 100% of one it with the while loop.

The switch statement has no wait loop so it doesnt consumes CPU.

Instead of waiting manually, just implement the Event-Based Asynchronous Pattern(EAP):

Mark Receiver() as void and thus return statement should be removed.
Declare an event on your DataManager class like "OperationDone".
Fire the event with the _outputList at the last step of the steate machine.
Capture the event to return the value.

Now the only CPU consumption will be done by the state machine framework.

Another usefull link: How to: Wrap EAP Patterns in a Task.

Stateless Statemachine Framework and high CPU usage

2 Answers2