QDebug prevents 100% CPU usage on boost::thread

Ayse

In code blocks , if I have no QDebug or printf on threads I get Figure 1, with QDebug I get sinusoid diagram on Figure 2. But I want to CPU usage like Figure 1, what caused this unexpected CPU usage , how can I prevent sinusoid CPU usage.

Figure 1.

Figure 2.

Thanks Regards..

boost::mutex mtx;
static int i =0;

void tFunc()
{
    while(true)
    {
        mtx.lock();
        ++i;
        mtx.unlock();
        // qDebug() = comment => CPU  %100?
        qDebug() << i;

    }
}
void tFunc2()
{
    while(true)
    {
        mtx.lock();
        ++i;
        mtx.unlock();        
        qDebug() << i;
    }
}
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    cpu_set_t set;
    // cpu_set_t : Data structure represents a set of CPUs.
    CPU_ZERO(&set);
    //CPU_ZERO : Clears set, so that it contains no CPUs.
    CPU_SET(0,&set); // CPU 1
    //CPU_SET : Add CPU to cpu set.  

    sched_setaffinity(0,sizeof(cpu_set_t),&set);

    boost::thread *tP2 = new boost::thread(tFunc);
    boost::thread *tP3 = new boost::thread(tFunc2);

 
    return a.exec();
}

SGaist

Hi,

It's not unexpected, printing something from your thread requires a lot more instructions and IO than just incrementing a counter that will happen in memory.

So if you want to maximise your CPU usage, don't print.