Thanks so much for the response.
So do I have this right then?
QTimer doesn't use any actually timers in the OS (no system
calls/interrupts). It is all handled internally by Qt's event loop. So if
the OS doesn't give Qt CPU time, it will miss a timer. Calling 'nice'
(Linux) on the process may help with this.
Josh
On quarta-feira, 26 de julho de 2017 12:58:43 PDT Joshua Grauman wrote:
Hello all,
I have a QTimer in my application that runs every 40ms. It doesn't run
continuously, but I recall the start function every time my timer function
is done so that the timer doesn't drift over time. My question though is
about timeout overrun. If the system is busy, and so the timer is late,
will Qt::PreciseTimer be more likely to return on time than
Qt::CoarseTimer? In other words, I'm ok with the 5% accuracy of
Qt::CoarseTimer normally (when the system isn't busy), but when the 40ms
timer is getting close to 60ms, I want to avoid timer overrun.
The type of timer is not relevant. All timers behave the same way: if it's
serviced as soon as it's available and the next wake up will always be the
current time + interval (± coarseness, if applicable).
Qt does not control when the OS gives us CPU time to service the timers. If
you need that, you need to consult your OS API and create a high-priority
thread or process, something that usually requires privilege elevation. Qt
cannot help you there.
Does anyone have any more precise info about Qt::PreciseTimer than the
docs which say:
"All timer types may time out later than expected if the system is busy
or unable to provide the requested accuracy. In such a case of timeout
overrun, Qt will emit activated() only once, even if multiple timeouts
have expired, and then will resume the original interval."
There is no more info to be had.
--
Thiago Macieira - thiago.macieira (AT) intel.com
Software Architect - Intel Open Source Technology Center
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