Question

I need a timer to be triggered every 1 ms. This document reports, that slot invocation may be much slower than even a virtual function call.

But if we compare signals/slots with event occurance, what mechanism will be faster, more efficient and produce less overhead: QTimer with it’s timeout() signal connected to a slot or bare QObject::startTimer()\ QObject::killTimer() with QObject::timerEvent()?

Will the answer for above question be the same for Windows and Linux?

Answer 1

QTimer is actually just a signal-slot wrapper around the QObject::startTimer() functionality, so it will undoubtedly have more overhead associated with it on all platforms (it internally implements QObject::timerEvent() — its implementation of this function is just to emit the timeout() signal).

Of note, QBasicTimer is a more light-weight wrapper around the QObject::startTimer() functionality. If you use QBasicTimer, you still have to implement QObject::timerEvent(), but it manages the timer ID for you. As such, a QBasicTimer combines some of the ease-of-use of a QTimer with the efficiency of using the QObject::startTimer() mechanism.