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

Jamie Bullock jamie at postlude.co.uk
Wed Apr 27 10:38:02 CEST 2005

On Wed, 2005-04-27 at 09:13 +0100, Jamie Bullock wrote:
> I don't have any scientific benchmarks, but FWIW, here is a bit of my
> experience with CCRMA.
> I have tried the stock FC3 kernel, built my own from vanilla sources +
> patches and now I use only CCRMA. I don't know about RH9, but the only
> significant difference between the stock FC3 kernel and the 'standard'
> CCRMA kernel  is that CCRMA includes the LSM (Linux Security Module),
> which allows non-root users to run applications with real time priority.
> This is a convenience and not a performance enhancement. It also
> introduces a security vulnerability, so it should be used with care if
> your machine is on a LAN.
> If you want serious a low latency, high performance system you need to
> go for one of the Planetedge kernels, which include Ingo Molnar's
> preemption patch. I don't use these, simply because I am happy with the
> latency/performance of my system already. 
> I run Jackd at 64 frames per
> perid (2 periods per buffer), which gives a system latency of around 3

No I don't, I run it at 128 fpp, which is more like 6ms - still good
though. You could probably get 64 with the edge kernel.

> ms. I can do everything I need, but if I'm doing real time OpenGL with
> Gem, and Audio, I down clock to 256 fpp, which is system latency of
> around 11ms.
> When you say just the kernel, do you mean the kernel and associated
> modules? If you switch to the CCRMA kernel, you will need to get the
> CCRMA ALSA drivers, and recompile any unique modules such as video
> wireless network.
> Also - you'll need root access to install the kernel unless you plan to
> boot from a usb key or CD, in any case you'll be able to install the
> apps as well, or am I missing something.
> Jamie
> On Tue, 2005-04-26 at 19:13 -0400, Mike Wozniewski wrote:
> > Hi.
> > 
> > I asked a similar question about Gem a little while back, but now I'd 
> > like to focus on audio alone.
> > 
> > Has anyone ever published performance results/benchmarks when using the 
> > Planet CCRMA kernel vs. a regular RedHat/Fedora kernel? Where can I find 
> > them?
> > 
> > ...or how about the benefit of using the -rt (realtime) option in Pd? I 
> > don't seem to notice a difference.
> > 
> > Is it worth it for me to install *just* the Planet CCRMA kernel for 
> > RedHat 9? ...note that I can't really install anything else since I'm on 
> > a networked machine with many restrictions. Will I get much improvement 
> > from just the kernel alone?
> > 
> > Also, is there a chance that the new kernel won't work with my existing 
> > (alsa-enabled) RedHat9 system? or could it break something so that I 
> > won't be able to return to my working system?
> > 
> > Thanks,
> > Mike Wozniewski
> > 
> > 
> > 
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