[LAU] What exactly is JACK DSP % usage ?

Paul Davis paul at linuxaudiosystems.com
Tue Feb 23 14:03:33 UTC 2016


Every N msecs, your audio interface wakes up the CPU to tell it to read and
write X samples of audio data. The CPU (and the OS) in turn wakes up JACK
to tell it do the same, along with any other processing that is part of
that.

If it takes JACK N msecs to finish the task, the DSP load is 100%.
If it takes JACK 0.0000001 msecs to finish the task, the DSP load is very
close to 0%.
If it takes JACK N/2 msecs to finish the task, the DSP load is 50%.

Values about 80% appear unstable/unusable on all 3 of Linux, OS X and
Windows.


On Tue, Feb 23, 2016 at 8:50 AM, Jonathan E. Brickman <jeb at ponderworthy.com>
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?
>
> --
> Jonathan E. Brickman   jeb at ponderworthy.com   (785)233-9977
> Hear us at http://ponderworthy.com -- CDs and MP3 now available!
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