Threading and CPU usage 100

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1.00/5 (1 vote)

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hi ,

how to use the infinite loop using threading....

while i am executing below code... it's taking 100 % usage of the CPU...

How i can reduce the CPU usage at-least 50 %

C#

namespace ThreadingIssue
{
    class Program
    {
        static void Main(string[] args)
        {
            ThreadStart ts = new ThreadStart(Test);
            Thread th = new Thread(ts);
            th.IsBackground = true;
            th.Priority = ThreadPriority.Lowest;
            th.Start();

            ts = new ThreadStart(Test1);
            th = new Thread(ts);
            th.IsBackground = true;
            th.Priority = ThreadPriority.Lowest;
            th.Start();

            Console.ReadKey();
        }

        static void Test()
        {
            while (true)
            {

            }
        }

        static void Test1()
        {
            while (true)
            {

            }
        }
    }
}

Posted 30-Mar-11 22:05pm

vijayr

Updated 30-Mar-11 22:06pm

Tarun.K.S

v2

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Comments

Sergey Alexandrovich Kryukov 31-Mar-11 14:35pm

Your while (true) loop is called spin-wait. There is no situations where it can be tolerated. Never ever.
--SA

4 solutions

Solution 4

You do not just sleep, you want to sleep on condition. The the answers with sleep won't help you.
You should never ever use spin wait. You should wait using thread synchronization primitives only.

Also, better not touch thread priority. If you do it right, it will not waste any CPU time. Here is how:

You need not sleep, you need to wait for System.Threading.EventWaitHandle.

Thread code is:

C#

MyEventWaitHandle.WaitOne();

Alternatively, you can use WaitOne with a parameter, which is a timeout.

On this call OS switches the thread off and never schedules it back to execution until it is waken up. The thread will spend exactly zero CPU time. The thread can be waken up only be MyEventWaitHandle.Set or Thread.Abort called from the other thread. That's it.

—SA

Posted 31-Mar-11 8:42am

Sergey Alexandrovich Kryukov

Updated 31-Mar-11 8:51am

v4

Comments

Olivier Levrey 1-Apr-11 3:56am

This answer is correct and definetly better than using Sleep. Have a 5.

Sergey Alexandrovich Kryukov 1-Apr-11 4:17am

Thank you, Olivier.
--SA

Solution 1

In these blocks, you're just in a really tight loop that's going to result in very high CPU

C#

while (true)
{
}

You could try putting the thread to sleep for a moment

C#

while (true)
{
    System.Threading.Thread.Sleep(100);
}

Posted 30-Mar-11 22:17pm

Dylan Morley

Comments

vijayr 31-Mar-11 4:24am

thanks for data... but the issue which i facing
eg ., While(true)
{
doing something based on the variable value which keep increment in another loop in the second thread...
}

Dylan Morley 31-Mar-11 4:25am

OK, please post code that will be in the loop - update your original question.

vijayr 31-Mar-11 4:50am

static int curSliderPos =0;
static void Test()
{
while (true)
{
//Based on the "curSliderPos" few operation will be there, which can't mention here :-(
}
}

static void Test1()
{
while (true)
{
//getting the video position and assign it in to the variable
curSliderPos = axWindowsmediaplayer.currentposition
}
}

Dylan Morley 31-Mar-11 4:52am

Sorry, if you can't mention code I can't offer any relevant advice

vijayr 31-Mar-11 4:56am

Anyway i was given a outline of the logic from the software...
is it not posible...

Thanks
Vijay r

Olivier Levrey 31-Mar-11 4:46am

My vote of 4. This answer will do quite OP is asking for, but I think you and OP missed the point: trying to lower CPU usage is just pointless and inefficient.

Sergey Alexandrovich Kryukov 31-Mar-11 14:48pm

Not a right thing as well. The only correct way is mine, please see.
--SA

Sergey Alexandrovich Kryukov 31-Mar-11 14:48pm

It works, but solution is pretty bad. You still do spin wait.

The ultimately correct solution does exist -- see my Answer.
--SA

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Olivier Levrey · Accepted Answer · 2011-03-30T22:44:00

Solution 2

100% CPU doesn't mean your program is not working properly, it just means it's using all the available CPU.

There is no sense to make your thread slower except to let the other threads be more responsive. But you already did it with ThreadPriority.Lowest. Changing the priority this way is the best way to make your program run as fast as possible and let the other threads responsive (UI and system threads).

Using System.Threading.Thread.Sleep(...) is good to let other threads work as well, but will slow down your own computations dramatically.

You have available CPU: why wouldn't you use it??? Just tell the system "my task is not so important" (as you did) and it will do the rest.

You could even go further and change the Process.PriorityClass if you need to.

------

I read your comments and I think what you are looking for is synchronization. If you access a variable from 2 different threads, you must secure its access with synchronization objects. Have a look to this link for example:
http://www.albahari.com/threading/part2.aspx[^]

Posted 30-Mar-11 22:44pm

Olivier Levrey

Updated 30-Mar-11 22:59pm

v5

Comments

vijayr 31-Mar-11 4:55am

Exactly i am agreed with ur point... but the issue is i can't use the sleep method because of the logic which behind in the software

Olivier Levrey 31-Mar-11 4:59am

I updated my answer.

Sergey Alexandrovich Kryukov 31-Mar-11 14:47pm

Sorry Olivier, I did not vote this time.
Sleep does not allow to wake up on condition, sleep time is unknown.
I put the ultimate solution in my Answer, please see.
--SA

Olivier Levrey 1-Apr-11 3:53am

I didn't say Sleep will "wake up on condition", I said "let other threads work". I didn't mean other threads in the application but other threads in the system which is as you known correct. And where did I write the sleep time was known?

Olivier Levrey 1-Apr-11 3:55am

And by the way I advised OP to use synchronization functions instead of sleep which is exactly what you said in your answer.

Sergey Alexandrovich Kryukov 1-Apr-11 4:10am

If so, I agree, voted 5.
--SA

Sergey Alexandrovich Kryukov 1-Apr-11 4:11am

By the way, do you see my April 1st post yet?

http://www.codeproject.com/Answers/175616/WARNING-Black-Line-of-Death-in-windows-phone-7.aspx

:-)

--SA

Olivier Levrey 1-Apr-11 4:20am

I didn't see before, thank you for sending the link: my day is starting nicely :)

SwitcherSoft · Accepted Answer · 2011-03-30T23:00:00

Hi , I agree with Dylan, you should add some kind of interval or sleep.

You can still use your code as you please, adding a 10ms wait will not slow down your computations.

Hope this helps.

I used an AutoResetEvent

Regards

Terence

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace ThreadingIssue
{
    class Program
    {
        static AutoResetEvent _AREvt;

        static void Main(string[] args)
        {

            _AREvt = new AutoResetEvent(false);

            ThreadStart ts = new ThreadStart(Test);
            Thread th = new Thread(ts);
            th.IsBackground = true;
            th.Priority = ThreadPriority.Lowest;
            th.Start();

            ts = new ThreadStart(Test1);
            th = new Thread(ts);
            th.IsBackground = true;
            th.Priority = ThreadPriority.Lowest;
            th.Start();

            Console.ReadKey();
        }

        static void Test()
        {
            
            while (true)
            {
             
                //do what you need todo
                _AREvt.WaitOne(10, true);

            }
        }

        static void Test1()
        {
            while (true)
            {
             
                //do what you need todo
                _AREvt.WaitOne(10, true);

            }
        }
    }
}

Threading and CPU usage 100

4 solutions

Solution 4

Solution 2

Solution 3

Solution 1

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