[LAU] What exactly is JACK DSP % usage ?

[Robin Gareus]

On 02/23/2016 02:50 PM, Jonathan E. Brickman wrote:
> Eight-core, 4GHz AMD, 8G RAM.  Running a lot of things all at once, 60
> high-demand tones out of two Yoshimis (120 total), JACK DSP % usage is
> 85%, but CPU usage through htop is a different thing, one CPU is being
> kept by one Yoshimi at 64%, the rest less than 15% and some down to
> 1-2%.  JACK is not stressing any CPU!
> 
> So my primary question is, what is JACK DSP % usage, what are its
> limiting factors?

DSP load is ratio of time it takes to perform audio i/o and process that
audio per cycle over the time between process cycles.

e.g. you run jack at 256 frames/period, 48KHz.
One process cycle is 5.5ms long.

The time it takes to for jack do read/write audio from/to the soundcard,
plus the time the two Yoshimi instances need to synthesize 256 samples
of audio in your case would be about about 4.5ms. (85% of those 5.5ms).

There are plenty of limiting factors to realtime operations on modern
multi-taking systems. Raw CPU power is usually the least concern.

http://manual.ardour.org/setting-up-your-system/the-right-computer-system-for-digital-audio/
is a starting point.

best,
robin