> > Message: 11 > Date: Wed, 6 Apr 2016 00:26:32 +0200 > From: Alexandre DENIS <contact@xxxxxxxxxxxxxxxxxx> > To: linux-audio-user@xxxxxxxxxxxxxxxxxxxx > Subject: Re: multiJACK patch management: the first glimmerings > of success > Message-ID: <20160406002632.19d7ee47@cocalight> > Content-Type: text/plain; charset="iso-8859-1" > > On Tue, 5 Apr 2016 22:27:46 +0200 > J?rn Nettingsmeier <nettings@xxxxxxxxxxxxxxxxxxx> wrote: > >> I have never used a graph as complex as Jonathan's, but I don't see >> how adding virtual machine and networking overhead could improve >> throughput when JACK2 should already parallelize everything that can >> be parallelized... Wouldn't the time be better spent to analyze >> JACK2's scheduling behaviour and catch bugs if there are any? > > Hi, > > Jack2 cannot parallelize processing if the graph is a pipeline: since > every stage depends on the data from previous stage, they must be run > in sequence. > > However, a pipeline may be parallelized if you trade parallelism > against latency. You can run each stage in parallel if they process > data from different periods. Jack2 doesn't do that by itself since it > would introduce uncontrolled latency. > > When you run multiple jackd and link them with netjack, you introduce > latency in the pipeline, which explains why you can have more > parallelism. However, it looks completely overkill to me and > introduces lots of overhead. > > I think it should be doable to write a simple client that connects as > two unrelated clients to jack, and feeds its outputs with its inputs > with one period of delay. It will make jack2 run the client connected > to its inputs and to its outputs in parallel, since jackd doesn't see > it as a dependency; but the latency of one period is unavoidable, since > we cannot predict whether jackd will invoke first the callback for the > inputs or for the output (or maybe at the same time on different > cores). Such a client should be no more than a few hundred lines of > code. > > -a. jackd2 has a « loopback » driver implemented since day 1 (OK maybe day 2….) - the code is in common/JackLoopbackDriver.cpp, h - it can be activated using the -L parameter like : jackd -L 4 -d also xxxxxx to add 4 loopback ports. Stéphane _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
