Re: [LAU] Question about DSP/Processor Load and multiproc support

On Sun, Oct 11, 2009 at 04:32:29PM +0200, Aurelien wrote:

> OK. (btw, how is defined the recent past?)

I would have to scan the sources to find out :-)

> Actually, I do not get any xruns, except when load just comes to 100%. I
> work with FFADO (unstable) on a Focusrite Saffire Pro 40, and have a
> quad-core machine with 8Gb. I mainly use synth (alsa modular x4),
> sooperlooper (2 stereo loopers, 2 mono), tapeutape and some (many) audio
> routing. I usually work around 80-85% (without sequencer playing) and 90
> % load. But sometimes (really not often), I've got this load increase
> and then an xrun. It could be widely sufficient if it wasn't purposed
> to play onstage, actually.

If you get a reliable 85% that is actually quite good
and it would seem unwise to want more, in particular for
live work. The actual amount of work done in a synth will
not be exactly constant, it may depend on the number of
active voices, or you may have algorithms that have a
complexity that depends on the signal itself, so you
should allow for some spare time. And the rest of your
system needs to run as well !

FFADO if I'm not mistaken is multi-threaded, and I suspect
its threads could be at lower priority than Jack's. You
can easily verify this with e.g. top (use 'H' to show
all threads). So if the jack clients don't leave enough
time to FFADO, it will get an xrun. You could try lowering
Jack's priority. That will not solve the problem, but the
result should be different - no xruns but probably Jack
reporting it doesn't get enough time to run all clients,
and maybe removing one of them.

BTW, on your quad-core you should be running jack2 aka
jackdmp. With jack1 and almost all load in audio apps
you are probably not exploiting the full power of your
machine.

Ciao,

-- 
FA
Io lo dico sempre: l'Italia è troppo stretta e lunga.
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