CODEWITHSUNDEEP
c#multithreadingperformanceasynchronous
Hooplator15
Hooplator15

Reputation: 1550

High CPU usage from while loop, checking for keypress event

I have a console application with two threads, one is doing repetitive time consuming work, the other is checking to see if the user has pressed the ESC key. If the ESC key was pressed, the time consuming work thread is paused, an "are you sure" message appears, and if yes is selected, the time consuming work thread finishes its current loop then exits.

The code I have to check for a key-press is using a lot of CPU resources due to the while (!breakCurrentOperation(work)) ; loop. How can I prevent this from happening?

Code: 

    public void runTimeConsumingWork()
    {
        HardWork work = new HardWork();

        Thread workerThread = new Thread(() => work.StartWorking());
        workerThread.Start(); // Start the hard work thread

        while (!workerThread.IsAlive) ; // Hault untill Thread becomes Active 

        // Check if the user wants to stop the hard work
        while (!breakCurrentOperation(work)) ;

        // Cancle the hard work
        work.Stop();

        // Notify the User
        UserInterfaceController.WriteToConsole("Operation Cancled...");
    }


    public static bool breakCurrentOperation(HardWork work)
    {
        if (Console.KeyAvailable)
        {
            var consoleKey = Console.ReadKey(true);
            if (consoleKey.Key == ConsoleKey.Escape)
            {
                work.Pause(); // Pause
                UserInterfaceController.WriteToConsole("Do you want to stop the current process? \nType s to stop or c to continue.");
                string input = Console.ReadLine();
                if (input == "c" || input == "C")
                {
                    work.Pause(); // Unpause
                    return false; // Continue 
                }
                else if (input == "s" || input == "S")
                {
                    return true; // Break the loop
                }
                else
                {
                    UserInterfaceController.WriteToConsole("Error: Input was not recognized, the current process will now continue. Press Esc to stop the operation.");
                    work.Pause(); // Unpause
                }
            }
        }
        return false;
    }

If I place a Thread.Sleep(2000) in the main console UI thread, CPU usage goes way down, but the application becomes unresponsive with a 2 second delay.

Upvotes: 3

Views: 1156

Answers (2)

Bradley Uffner
Bradley Uffner

Reputation: 17001

Do you really have to constantly poll for input? If you are waiting for input in a separate thread, just use the Console.ReadKey. It will block the input thread, but your other thread will keep processing. You don't seem to be doing anything else on the input thread, so blocking shouldn't be an issue.

Upvotes: 3

Avinash Jain
Avinash Jain

Reputation: 7616

Look like your esc key press check logic running in end less loop due to while loop. Due to this the function keep utilizing the system resource.

To overcome this please use some delay in your loop using Thread.Sleep. 1 second delay will improve lot of performance.

Upvotes: 0

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