[LAU] what is jackd "DSP load"? Blinking "RT" indicator?

[Peter P.]

* Joakim Hernberg <jhernberg at alchemy.lu> [2014-09-04 10:09]:
> On Thu, 4 Sep 2014 09:03:55 -0400
> "Peter P." <p8rpp at aol.com> wrote:
> 
> > after many years of wondering now and then I am curious what
> > qjackctl's display of "DSP load" is supposed to mean?
> > It must be some kind of CPU load, as there is no dedicated DSP in my
> > computer, so is it the cpu load of the jackd process?
> > Furthermore I wonder why the realtime "RT" indicator in qjackctl's
> > window is blinking about every 2 seconds. I do have -rt enabled.
> 
> qjackctl's "DSP load" refers to how much of the latency given by
> samplerate and buffersize has been used up by the audio processing
> callback.  That is to say if you have 2.9ms to finish the audio
> processing, and the callback takes 1.45ms, then it will
> show 50%, if it takes 2.9ms then it will show 100%.  Note that it's an
> average and not a maximum number, so conventional wisdom is to keep it
> under 60% or so, to avoid xruns (ymmw).
> 
> The flashing RT just indicates that JACK is running in rt mode.
Joakim, Hermann, thanks to both of you for these excellent answers!
best, P