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c++multithreadingqtqt5affinity

How can I set a thread's CPU affinity in Qt5?

Working with threads in Qt5, how can I set a single thread's CPU affinity?

I want to specify a mask of available CPU cores that the thread may run under.

In other words, what is the Qt5 equivalent to Posix thread's pthread_setaffinity_np() ?

Can I do this for threads managed by QThreadPool?

Solution

  • Usually that sort of things is done by extracting the native thread handle and then doing whatever system specific stuff necessary, as no accepted cross-platform API exists for low level thread management.

    Indeed, if we inspect the source for the qthread_unix.cpp we will see the following:

    Qt::HANDLE QThread::currentThreadId() Q_DECL_NOTHROW
{
    // requires a C cast here otherwise we run into trouble on AIX
    return to_HANDLE(pthread_self());
}

    And in qthread_win.cpp the implementation will differ in the expected way:

    Qt::HANDLE QThread::currentThreadId() Q_DECL_NOTHROW
{
    return reinterpret_cast<Qt::HANDLE>(quintptr(GetCurrentThreadId()));
}

    So, it is responsibility of the application code to do the proper low level actions pertaining to each platform it is expected to run on.