[PD] benefits of planet ccrma kernel, and realtime priority pd?

Jamie Bullock jamie at postlude.co.uk
Wed Apr 27 21:14:45 CEST 2005


On Wed, 2005-04-27 at 13:36 -0400, Mike Wozniewski wrote:
> By just the kernel, I meant I didn't want to install any of the 
> packages. We are building a pretty heavy application with Pd+Gem. We 
> already have a decently working system. But any extra performance we can 
> get out of our current machines is beneficial. The graphics end is quite 
> optimized - so now I'm focusing on audio. I was wondering what kind of 
> benefit CCRMA could give. It seems from the emails that it's more of a 
> convenience benefit than performance (ie, it's easier to download 
> packages, run -rt without being root, etc.)... If I can run pd as root 
> anyway, it's not going to benefit me that much right?
AFAIK, the latency improvements are gained through improved scheduling.
I.E., the preemption patch allows for one process to be pre-empted by
another higher priority process. You can therefore make anything to do
with audio have absolute priority on your system, and this improves
latency etc. Unfortunately, this can be at the expense of other
processes, and sometimes overall stability. If you want to run audio and
real time graphics, you might end up optimising audio at the expense of
graphics, and this would presumably be bad.

I hope this helps,


> I guess though, that latency is a bit different from performance. It 
> sounds like the latency can be cut down a bit by CCRMA. Performance 
> however - ie, CPU load - is unaffected right? Julien, you said that 
> operating at lower latencies you get clicks when CPU load >80% ...does 
> this mean that in fact low latency might hinder a heavily loaded 
> application?
> Thanks again for your responses,
> -Mike

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