[PD] Real-time Linux; hard req. and suggestions?

David Merrill dmerrill at media.mit.edu
Fri Sep 8 20:46:50 CEST 2006


Hello all,

As has been mentioned, installing planet CCRMA is probably the easiest 
way to get out-of-the-box good latency. I've been using Ubuntu linux 
recently though, since I like how easy they're making it to 
install/update/configure (finally!). ubuntustudio.com is a resource that 
I've found for setting up Ubuntu linux for audio work.
http://ubuntustudio.com/wiki/index.php/Welcome%2C_Musicians%21

On the front page they mention Mubuntu, an alleged multimedia derivitave 
of Ubuntu, that is still in the works.
https://wiki.ubuntu.com/Mubuntu

I've been using Ubuntu for PD with pretty good latency results - by 
applying the realtime/preemptive patch I got my [adc~] -> [dac~] latency 
down to about 8msec. This was for the "Breezy" distro of Ubuntu, and the 
explanation of how to do it is here:
http://ubuntustudio.com/wiki/index.php/Breezy:Vanilla_Kernel_With_Realtime_Preemption

Now that I've updated to the lateset Ubuntu (Dapper), the how-to no 
longer applies, but I think I'm still getting decent latency, running pd 
with the -rt flag.
-David M.

Frank Barknecht wrote:
> Hallo,
> Charles Henry hat gesagt: // Charles Henry wrote:
>
>   
>> I've started learning a bit about alternative kernels for real-time
>> linux, and I've got some masochistic notion to investigate Linux From
>> Scratch.  One of my friends says this is his favorite way to build a
>> system...I have a lot to learn.
>> I'm currently using Fedora Core 4 with the 2.4.19 kernel on a 1.6 GHz
>> Sempron processor (could be upgraded to an Athlon64).  I'm not sure
>> which system specs are most important for getting good throughput,
>> front side bus, memory access speed...how to balance them?
>>     
>
> If you run a stock 2.4 kernel you will get really bad latency
> behaviour. You can fix this by using some realtime-patched 2.4 kernel
> but I would recommend to go a different route: Just install a recent
> 2.6 kernel, enable preemptible kernel etc. in the config and live happily
> with it.
>
> Stock 2.6 kernels now have excellent latency behaviour in the range of
> 1-3 msec. The so called "hard realtime" latency that can be achieved
> with Ingo Molnar's rt-patches will give latencies even below that, but
> do you really need them? In my opninion most Pd users don't need them
> and the time spend figuring out a good combination of rt-patch version
> and kernel version is better spent optimizing your Pd patches.
>
> Use Linux from Scratch if you are bored and have too much time on your
> hands. It will not give you relevantly better performance and IMO is
> not worth the effort. If you like to watch the output of make and gcc,
> Gentoo will satisfy you as well, but if you rather spend your time
> using, than compiling software, something like Fedora, Ubuntu or
> Debian (my fav.) is a better choice. 
>
> Ciao
>   


-- 
MIT Media Lab
dmerrill at media.mit.edu





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