[linux-audio-dev] Linux Security Module for realtime audio

[Benno Senoner]

Jens M Andreasen wrote:

>If the GUI is not running in realtime, then things like changing the
>patch number from the midi stream won't be reflected instantaniously on
>screen. To the contrary: You can almost imagine SuperMario running up
>and down the interface with his little brushes, slowly repainting each
>and every knob and slider :-) This happens even if the realtime audio
>engine is near idle. 
>
>The audio engine can still have priority over the GUI. That is to say:
>The GUI is another realtime process albeit with a much lower priority
>(than the audio engine.)
>
>  
>
Jens I disagree here: given the slowness of X11 and/or some gfx card/PC 
combination,
if you run the GUI process with real time privileges, you can run into 
situations where
the box becomes unusable because the GUI uses up all the available CPU.
(Imagine a sequencer updating dozen of pianorolls, volume peak meters, 
FFT displays etc,
this can easily bring a 2GHz box on its knees).
So what I propose is to run the GUI with some negative nice value, eg 
-10 but not
with SCHED_FIFO/RR.

Plus if the machine is under high load because the audio thread uses up 
90% of the CPU then
even running the GUI with real time scheduling won't chane anything, 
repaints would still be slow.

Benno
http://www.linuxsampler.org