[linux-audio-user] dual-core and jack question

[Paul Davis]

On Thu, 2007-03-01 at 15:06 +0100, Robert Jonsson wrote:
> Possibly I'm missing something here, but I was under the impression that 
> to _really_ utilize a dual core system you need to use Jackdmp.
> Jackd will only use one core. The other core won't be without work 
> though, there's plenty of work to redraw gui's and what not.
> Someone do correct me if I'm wrong.

no, thats basically correct. in jackd, the JACK threads of every client
will be serialized. this means that audio processing will happen on one
CPU at a time (not necessarily the same one). as you said, however, this
hardly means that the other CPU(s) are idle, they just don't get used
for audio processing.

note that jackdmp can only use more than 1 CPU if there are parallel
data flows in the audio connections. for example, this will not use
multiple cores:

	freqtweak -> sooperlooper -> timemachine

neither will

	ardour -> jamin

however, this will:

	zynaddsubfx ----+
                        |
	                +------> ardour
                        |
        bristol --------+

audio data processing is rarely as inherently parallel as, say,
graphics.

--p